Systems and methods to facilitate location determination by beamforming of a positioning reference signal

ABSTRACT

Techniques are provided for positioning of a mobile device in a wireless network using directional positioning reference signals (PRS), also referred to as PRS beamforming. In an example method, a plurality of directional PRSs are generated for at least one cell for a base station, such that each of the plurality of directional PRSs comprises at least one signal characteristic and a direction of transmission, either or both of which may be distinct or unique. The plurality of directional PRSs is transmitted within the at least one cell, such that each of the plurality of directional PRSs is transmitted in the direction of transmission. A mobile device may acquire and measure at least one of the directional PRSs which may be identified using the associated signal characteristic. The measurement may be used to assist position methods such as OTDOA and ECID and to mitigate multipath.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.17/743,431, filed May 12, 2022, entitled “SYSTEMS AND METHODS TOFACILITATE LOCATION DETERMINATION BY BEAMFORMING OF A POSITIONINGREFERENCE SIGNAL,” which is a continuation of U.S. patent applicationSer. No. 16/782,119, now U.S. Pat. No. 11,496,990, filed Feb. 5, 2020,entitled “SYSTEMS AND METHODS TO FACILITATE LOCATION DETERMINATION BYBEAMFORMING OF A POSITIONING REFERENCE SIGNAL,” which is a continuationof U.S. application Ser. No. 15/866,538, now U.S. Pat. No. 10,736,074,filed Jan. 10, 2018, entitled “SYSTEMS AND METHODS TO FACILITATELOCATION DETERMINATION BY BEAMFORMING OF A POSITIONING REFERENCESIGNAL,” which claims the benefit of U.S. Provisional Application No.62/538,952, filed Jul. 31, 2017, entitled “SYSTEMS AND METHODS TOFACILITATE LOCATION DETERMINATION BY BEAMFORMING OF A POSITIONINGREFERENCE SIGNAL,” each of which is assigned to the assignee hereof andof which the entire contents are hereby incorporated herein by referencefor all purposes.

BACKGROUND

Obtaining the location or position of a mobile device that is accessinga wireless network may be useful for many applications including, forexample, emergency calls, personal navigation, asset tracking, locatinga friend or family member, etc. Existing position methods includemethods based on measuring radio signals transmitted from a variety ofdevices including satellite vehicles (SVs) and terrestrial radio sourcesin a wireless network such as base stations and access points. Inmethods based on terrestrial radio sources, a mobile device may measurethe timing of signals received from two or more base stations anddetermine times of arrival, time differences of arrival and/or receivetime-transmit time differences. Combining these measurements with knownlocations for the base stations and known transmission times from eachbase station may enable location of the mobile device using suchposition methods as Observed Time Difference Of Arrival (OTDOA) orEnhanced Cell ID (ECID).

To further help location determination (e.g. for OTDOA), PositioningReference Signals (PRS) may be transmitted by base stations in order toincrease both measurement accuracy and the number of different basestations for which timing measurements can be obtained by a mobiledevice. However, location accuracy may be impaired by a number offactors including errors, imprecision in location measurements andmultipath effects, where a PRS signal may be reflected, refracted orscattered by intervening obstacles such as trees, walls, buildings andtraffic. Methods and techniques to mitigate or overcome such factors maythus be beneficial.

SUMMARY

An example of a method, at a first base station, for supportingpositioning of a mobile device, according to the disclosure includesgenerating a plurality of directional positioning reference signals(PRSs) for at least one cell for the base station, such that each of theplurality of directional PRSs comprises at least one signalcharacteristic and a direction of transmission, and transmitting theeach of the plurality of directional PRSs within the at least one cell,such that each of the plurality of directional PRSs is transmitted inthe direction of transmission.

Implementations of such a method may include one or more of thefollowing features. The at least one signal characteristic may include afrequency, a frequency shift, a code sequence, a muting pattern, atransmission time, or any combination thereof. Transmitting theplurality of directional PRSs within the at least one cell may includedirecting the plurality of directional PRSs through a controllableantenna array configured to beamform each directional PRS in thedirection of transmission. The direction of transmission may include acontinuous range of horizontal angles, a continuous range of verticalangles, or a combination thereof. At least one of the plurality ofdirectional PRSs may be detectable by the mobile device to facilitatelocation determination of the mobile device at a location-capable devicebased on an observed time difference of arrival (OTDOA) position method,an angle of departure (AOD) position method, or an Enhanced Cell ID(ECID) position method, or any combination thereof. The at least one ofthe plurality of directional PRSs may be detectable by the mobile devicebased on the direction of transmission for the at least one of theplurality of directional PRSs, the at least one signal characteristicfor the at least one of the plurality of directional PRSs, or acombination thereof. The method may further include sending at least oneof the direction of transmission for the at least one of the pluralityof directional PRSs or the at least one signal characteristic for the atleast one of the plurality of directional PRSs to the mobile device. Thesending may be based on broadcast within the at least one cell. Thelocation determination at the location-capable device may includedetermining a presence or absence of multipath for the least one of theplurality of directional PRSs based on a direction of transmission forthe least one of the plurality of directional PRSs and an approximatelocation for the mobile device, such that determining the location ofthe mobile device at the location-capable device is based, at least inpart, on the determined presence or absence of multipath. Theapproximate location for the mobile device may be based, at least inpart, on a serving cell for the mobile device. The location-capabledevice may include a second base station different to the first basestation, the mobile device or a Location Management Function (LMF), andsuch that the method further includes sending the direction oftransmission for the at least one of the plurality of directional PRSsto the location-capable device. The at least one cell may be a servingcell for the mobile device. At least one of the at least one signalcharacteristic and the direction of transmission for each of theplurality of directional PRSs may be unique.

An example of a method, at a mobile device, for supporting positioningof the mobile device, according to the disclosure includes receiving, atthe mobile device, a first directional positioning reference signal(PRS) transmitted by a first base station within at least one cell forthe first base station, such that the first directional PRS comprises atleast one first signal characteristic and a first direction oftransmission, obtaining at least one first measurement for the firstdirectional PRS based, at least in part, on the at least one firstsignal characteristic, and facilitating location determination of themobile device at a location-capable device based, at least in part, onthe at least one first measurement.

Implementations of such a method may include one or more of thefollowing features. The at least one first signal characteristic mayinclude a carrier frequency, a frequency shift, a code sequence, amuting pattern, a bandwidth, a transmission time, or any combinationthereof. The first directional PRS may be transmitted from the firstbase station through a controllable antenna array configured to beamformthe first directional PRS in the first direction of transmission. Thefirst direction of transmission may include a continuous range ofhorizontal angles, a continuous range of vertical angles, or acombination thereof. The method may further include receiving the atleast one first signal characteristic for the first directional PRS fromthe first base station or from a Location Management Function (LMF). Theat least one first measurement for the first directional PRS may includea Time Of Arrival (TOA), a Reference Signal Time Difference (RSTD), aReceived Signal Strength Indication (RSSI), a Reference Signal ReceivedPower (RSRP), a Reference Signal Received Quality (RSRQ), an Angle ofArrival (AOA), a signal propagation time, a detection of the at leastone signal characteristic, or any combination thereof. The locationdetermination of the mobile device at the location-capable device may bebased on an observed time difference of arrival (OTDOA) position method,an angle of departure (AOD) position method, or an Enhanced Cell ID(ECID) position method, or any combination thereof. The locationdetermination of the mobile device at the location-capable device mayinclude determining a presence or absence of multipath for the firstdirectional PRS based on the first direction of transmission and anapproximate location for the mobile device, such that determining thelocation of the mobile device at the location-capable device is based,at least in part, on the determined presence or absence of multipath.The approximate location for the mobile device may be based, at least inpart, on a serving cell for the mobile device. The location-capabledevice may include the first base station, or a Location ManagementFunction (LMF), and such that the method further includes sending the atleast one first measurement for the first directional PRS to thelocation-capable device. The method may include receiving, at the mobiledevice, a second directional PRS transmitted by a second base stationwithin at least one cell for the second base station, such that thesecond directional PRS comprises at least one second signalcharacteristic and a second direction of transmission, and such that theat least one second signal characteristic and the second direction oftransmission for the second directional PRS are, respectively, differentfrom the at least one first signal characteristic and the firstdirection of transmission for the first directional PRS, obtaining atleast one second measurement for the second directional PRS based, atleast in part, on the at least one second signal characteristic for thesecond directional PRS, and facilitating location determination of themobile device at the location-capable device based, at least in part, onthe at least one first measurement and the at least one secondmeasurement. The at least one cell for the first base station may be aserving cell for the mobile device. At least one of the at least onefirst signal characteristic and the first direction of transmission forthe first directional PRS may be unique.

An example of a method, at a location-capable device, for supportingpositioning of a mobile device, according to the disclosure includesobtaining at least one first measurement from the mobile device for afirst directional positioning reference signal (PRS) transmitted by afirst base station in at least one cell for the first base station, suchthat the first directional PRS comprises at least one first signalcharacteristic and a first direction of transmission, and determiningthe location of the mobile device based, at least in part, on the atleast one first measurement and the first direction of transmission.

Implementations of such a method may include one or more of thefollowing features. The at least one first signal characteristic mayinclude a carrier frequency, a frequency shift, a code sequence, amuting pattern, a bandwidth, a transmission time, or any combinationthereof. The first directional PRS may be transmitted from the firstbase station through a controllable antenna array configured to beamformthe first directional PRS in the first direction of transmission. Thefirst direction of transmission may include a continuous range ofhorizontal angles, a continuous range of vertical angles, or acombination thereof. The location-capable device may include the mobiledevice, and such that the method further includes receiving the at leastone first signal characteristic and the first direction of transmissionfrom the first base station or from a Location Management Function(LMF). The first direction of transmission may be received from thefirst base station by receiving a broadcast signal from the first basestation. The location-capable device may include the first base station,or a Location Management Function (LMF), and such that the methodfurther includes receiving the at least one first measurement from themobile device. The method may also include sending the at least onefirst signal characteristic to the mobile device. The at least one firstmeasurement for the first directional PRS may include a Time Of Arrival(TOA), a Reference Signal Time Difference (RSTD), a Received SignalStrength Indication (RSSI), a Reference Signal Received Power (RSRP), aReference Signal Received Quality (RSRQ), an Angle of Arrival (AOA), asignal propagation time, a detection of the at least one first signalcharacteristic, or any combination thereof. Determining the location ofthe mobile device may be based on an observed time difference of arrival(OTDOA) position method, an angle of departure (AOD) position method, oran Enhanced Cell ID (ECID) position method, or any combination thereof.The method may include determining a presence or absence of multipathfor the first directional PRS based on the first direction oftransmission and an approximate location for the mobile device, suchthat determining the location of the mobile device is based, at least inpart, on the determined presence or absence of multipath. Theapproximate location for the mobile device may be based, at least inpart, on a serving cell for the mobile device. The method may includeobtaining at least one second measurement from the mobile device for asecond directional PRS transmitted by a second base station in at leastone cell for the second base station, such that the second directionalPRS comprises at least one second signal characteristic and a seconddirection of transmission, and such that the at least one second signalcharacteristic and the second direction of transmission for the seconddirectional PRS are, respectively, different from the at least one firstsignal characteristic and the first direction of transmission for thefirst directional PRS, and determining the location of the mobile devicebased, at least in part, on the at least one first measurement, the atleast one second measurement, the first direction of transmission forthe first directional PRS and the second direction of transmission forthe second directional PRS. The at least one cell for the first basestation may be a serving cell for the mobile device. At least one of theat least one first signal characteristic and the first direction oftransmission for the first directional PRS may be unique.

Other and further objects, features, aspects, and advantages of thepresent disclosure will become better understood with the followingdetailed description of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example communication system.

FIG. 2 is a diagram of an example configuration of beamformed(directional) positioning reference signals (PRS) transmitted from abase station.

FIG. 3A is a diagram illustrating an example implementation of usingdirectional (beamformed) PRS signals for location determinationfunctionality.

FIG. 3B is a diagram illustrating another example implementation ofusing directional PRS signals to facilitate location determinationfunctionality.

FIG. 4 is a diagram illustrating mitigation of multipath effects using adirectional PRS signal.

FIG. 5 is a signaling flow diagram showing messages sent betweencomponents of a communication network during a location session.

FIG. 6 is a diagram of a structure of an example LTE subframe sequencewith PRS positioning occasions.

FIG. 7 is a diagram illustrating further aspects of PRS transmission fora cell supported by a wireless node.

FIG. 8 is a flowchart of an example procedure, generally performed at anetwork node, to support and facilitate positioning of a mobile device.

FIG. 9 is a flowchart of an example procedure, generally performed at amobile device, to facilitate positioning of the mobile device.

FIG. 10 is a flowchart of an example procedure, generally performed at alocation-capable device, to facilitate positioning of a mobile device.

FIG. 11 is a schematic diagram of an example wireless node (such as abase station, access point, or server).

FIG. 12 is a schematic diagram of a mobile device (e.g., a UE).

Like reference symbols in the various drawings indicate like elements,in accordance with certain example implementations. In addition,multiple instances of an element may be indicated by following a firstnumber for the element with a hyphen and a second number or by a letter.For example, multiple instances of an element 110 may be indicated as110-1, 110-2, 110-3 etc. and/or as 110a, 110b, 110c etc. When referringto such an element using only the first number, any instance of theelement is to be understood (e.g. elements 110 in the previous examplewould refer to elements 110-1, 110-2 and 110-3 and/or to 110a, 110b and110c).

DETAILED DESCRIPTION

Obtaining the location or position of a mobile device that is accessinga wireless network may be useful for many applications including, forexample, emergency calls, personal navigation, asset tracking, locatinga friend or family member, etc. Existing position methods includemethods based on measuring radio signals transmitted from a variety ofdevices including satellite vehicles (SVs) and terrestrial radio sourcesin a wireless network such as base stations and access points. Inmethods based on terrestrial radio sources, a mobile device may measurethe timing of signals received from two or more base stations anddetermine signal strengths, times of arrival, time differences ofarrival and/or receive time-transmit time differences. Combining thesemeasurements with known locations for the base stations and possiblyknown transmission times from each base station may enable location ofthe mobile device using such position methods as Observed TimeDifference Of Arrival (OTDOA) or Enhanced Cell ID (ECID). Suchterrestrial based position methods may be employed in wireless networksthat support different wireless technologies such as Long Term Evolution(LTE) and Fifth Generation (5G) (also referred to as New Radio (NR)) asdefined by an organization known as the Third Generation PartnershipProject (3GPP).

Described herein are systems, devices, methods, media and otherimplementations for directional positioning reference signals (PRS),also referred to as PRS beamforming. PRS signals are used to supportpositioning using, for example, the OTDOA position method, and may betransmitted for different cells in a network at the same set of times orat different sets of times. For example, in the case of LTE access, aPRS may be transmitted during PRS positioning occasions which may occurat fixed periodic intervals, with each positioning occasion comprisingone or more consecutive subframes (e.g., LTE subframes of 1 ms durationeach). Cells using the same carrier frequency may be synchronized anduse PRS positioning occasions that occur at the same set of times.Although this would normally create interference in the case of othersignals, a PRS for any cell can be made non-interfering with (e.g.orthogonal to) the PRS for any other nearby cell. This can be achievedusing: (i) a different sequence of frequency subcarriers acrossconsecutive OFDM symbols in an LTE subframe (referred to as a frequencyshift or vshift), (ii) a different PRS code sequence, (iii) a differentmuting sequence in which PRS positioning occasions are muted accordingto a different periodic muting pattern, and/or (iv) differenttransmission times (e.g. which may be a variant of (iii)).

In the case of LTE or 5G communication technologies, a PRS may also bemade non-interfering with (e.g. orthogonal to) another PRS bybeamforming, using, for example, an antenna array at a base station(e.g. an eNodeB for LTE or a gNB for 5G). With beamforming, a signal(e.g., a PRS) is broadcast over a narrow continuous range of horizontaland/or vertical directions, e.g., directions with a horizontal span of 5or 10 degrees (or smaller or larger). Transmitting different signalsover a small angular range within a cell may also be referred to asspatial multiplexing. Similar to other approaches used to inhibit orprevent interference of PRS from different cells, a first directional(beamformed) PRS can be made non-interfering with any other seconddirectional PRS transmitted from the same base station by ensuring thatthe directions in which the first directional PRS is transmitted are alldifferent to the directions in which the second directional PRS istransmitted. When this non-interfering condition is achieved, thedirection of transmission for the first directional PRS may beconsidered as, and may be referred to as being, unique (in the contextof transmission from the given base station). In practice, achievingperfect non-interference may be difficult or impossible due to theexistence of side lobes and back lobes. Hence, a first directional PRSmay be considered to be, and may be referred to as being, transmitted ina unique direction when the signal strength for any second directionalPRS transmitted by the same base station is substantially weaker in thisparticular unique direction (e.g. weaker by at least 10 decibels (dB)).

A directional PRS may have other signal characteristics, in addition toa unique direction of transmission, which allow it to be distinguishedfrom another directional PRS and other non-directional PRS (e.g.transmitted throughout a cell coverage area). These other signalcharacteristics may include a particular carrier frequency, a particularfrequency shift (or vshift), a particular PRS code sequence, aparticular muting sequence, a particular bandwidth, and/or a particularset of transmission times. One of more of these signal characteristicsmay be different to the corresponding signal characteristics for otherdirectional PRS and/or other non-directional PRS transmitted by the samebase station and/or by other nearby base stations. When a particularfirst signal characteristic for a first directional PRS differs from acorresponding second signal characteristic for any other seconddirectional PRS transmitted from the same base station and/or from othernearby base stations, the first signal characteristic may be consideredas, and may be referred to as being, unique. When a particular firstcombination of two or more different signal characteristics for a firstdirectional PRS differ from a second combination of two or morecorresponding signal characteristics for any other second directionalPRS transmitted from the same base station and/or from other nearby basestations, the first combination of two or more signal characteristicsmay be considered as, and may be referred to as being, unique.

A unique signal characteristic or a unique combination of signalcharacteristics may enable a directional PRS to be identified by both amobile device and a location-capable device such as a location server.For example, a directional PRS may be defined according to its signalcharacteristics which may include a particular unique signalcharacteristic or a particular unique combination of signalcharacteristics and may further be assigned an identifier (ID) such aPRS ID, a transmission point (TP) ID or physical cell ID (PCI). Such anidentifier may also be used to identify a non-directional PRS that isbroadcast throughout a cell, which may avoid the need to define andimplement different types of identifiers for directional PRS andnon-directional PRS. By detecting and measuring a directional PRS thathas a given unique signal characteristic or a given unique combinationof signal characteristics and a unique identifier, a UE can be bothaware of which directional PRS has been measured and can identify thedirectional PRS to a location-capable device such as a location serverusing the unique identifier (e.g. when any measurement for thedirectional PRS is provided by the UE to the location-capable device).

The implementations described herein include a method, at a first basestation or other processor-based wireless node, for supportingpositioning of a mobile device (e.g. a UE), with the method includinggenerating a plurality of directional PRSs for at least one cell for thefirst base station, with each of the plurality of directional PRSscomprising at least one signal characteristic and a direction oftransmission, and transmitting the each of the plurality of directionalPRSs within the at least one cell, with each of the plurality ofdirectional PRSs being transmitted in the direction of transmission. Theat least one signal characteristic for a particular directional PRS maybe indicative of the respective direction of transmission for thatparticular directional PRS. The direction of transmission for theparticular directional PRS may be a unique or distinctive direction froma continuous range of horizontal angles, a continuous range of verticalangles, or a combination thereof. In some embodiments, the at least onesignal characteristic may include one or more of, for example, afrequency shift, a PRS code sequence, a muting pattern, and/or atransmission time. In some embodiments, transmitting the plurality ofdirectional PRSs within the at least one cell may include directing theplurality of directional PRSs through a controllable antenna arrayconfigured to beamform each directional PRS in the direction oftransmission. At least one of the plurality of directional PRSs may bedetectable by the mobile device to facilitate location determination ofthe mobile device at a location-capable device (which may be one or moreof the first base station, another base station, the mobile device, or aLocation Management Function (LMF)) based on an observed time differenceof arrival (OTDOA) position method, an angle of departure (AOD) positionmethod, or an Enhanced Cell ID (ECID) position method, or anycombination thereof.

Also described herein are systems, devices, methods, media, and otherimplementations to facilitate positioning of a mobile device, includinga method comprising receiving, at the mobile device, a first directionalPRS transmitted by a first base station within at least one cell for thefirst base station, with the first directional PRS comprising at leastone signal characteristic and a direction of transmission, and obtainingat least one first measurement for the first directional PRS based, atleast in part, on the at least one signal characteristic. The methodfurther includes facilitating location determination of the mobiledevice at a location-capable device based, at least in part, on the atleast one first measurement. Also disclosed are methods, systems, media,devices, and other implementations, including a method, at alocation-capable device, for supporting positioning of a mobile device,with the method including obtaining at least one first measurement fromthe mobile device for a first directional PRS transmitted by a firstbase station in at least one cell for the first base station, where thefirst directional PRS comprises at least one signal characteristic and adirection of transmission. The method further includes determining thelocation of the mobile device based, at least in part, on the at leastone first measurement and the direction of transmission. Thelocation-capable device may include one or more of, the first basestation, another base station, the mobile device, and/or a locationserver (such as an LMF).

FIG. 1 shows a diagram of a communication system 100, according to anembodiment. The communication system 100 may be configured to implementdirectional PRS transmission and reception. Here, the communicationsystem 100 comprises a user equipment (UE) 105, and components of aFifth Generation (5G) network comprising a Next Generation (NG) RadioAccess Network (RAN) (NG-RAN) 135 and a 5G Core Network (5GC) 140. A 5Gnetwork may also be referred to as a New Radio (NR) network; NG-RAN 135may be referred to as a 5G RAN or as an NR RAN; and 5GC 140 may bereferred to as an NG Core network (NGC). Standardization of an NG-RANand 5GC is ongoing in 3GPP. Accordingly, NG-RAN 135 and 5GC 140 mayconform to current or future standards for 5G support from 3GPP. Thecommunication system 100 may further utilize information from satellitevehicles (SVs) 190 for a Global Navigation Satellite System (GNSS) likeGPS, GLONASS, Galileo or Beidou or some other local or regionalSatellite Positioning System (SPS) such as IRNSS, EGNOS or WAAS.Additional components of the communication system 100 are describedbelow. The communication system 100 may include additional oralternative components.

It is noted that FIG. 1 provides only a generalized illustration ofvarious components, any or all of which may be utilized as appropriate,and each of which may be duplicated or omitted as necessary.Specifically, although only one UE 105 is illustrated, it will beunderstood that many UEs (e.g., hundreds, thousands, millions, etc.) mayutilize the communication system 100. Similarly, the communicationsystem 100 may include a larger (or smaller) number of SVs 190, gNBs110, ng-eNBs 114, AMFs 115, external clients 130, and/or othercomponents. The illustrated connections that connect the variouscomponents in the communication system 100 include data and signalingconnections which may include additional (intermediary) components,direct or indirect physical and/or wireless connections, and/oradditional networks. Furthermore, components may be rearranged,combined, separated, substituted, and/or omitted, depending on desiredfunctionality.

While FIG. 1 illustrates a 5G-based network, similar networkimplementations and configurations may be used for other communicationtechnologies, such as 3G, Long Term Evolution (LTE), etc.Implementations described herein (be they for 5G technology or for othercommunication technologies and protocols) may be used to transmit (orbroadcast) directional PRSs from base stations (e.g. gNBs 110, ng-eNBs114), receive and measure directional PRSs at UEs (e.g. UE 105) andcompute a location for a UE 105 at a location-capable device such as theUE 105, a gNB 110 or LMF 120 based on measurements at the UE 105 fordirectional PRSs.

The UE 105 may comprise and/or may be referred to as a device, a mobiledevice, a wireless device, a mobile terminal, a terminal, a mobilestation (MS), a Secure User Plane Location (SUPL) Enabled Terminal(SET), or by some other name. Moreover, UE 105 may correspond to acellphone, smartphone, laptop, tablet, PDA, tracking device, navigationdevice, Internet of Things (IoT) device, or some other portable ormoveable device. Typically, though not necessarily, the UE 105 maysupport wireless communication using one or more Radio AccessTechnologies (RATs) such as Global System for Mobile communication(GSM), Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), LTE,High Rate Packet Data (HRPD), IEEE 802.11 WiFi (also referred to asWi-Fi), Bluetooth® (BT), Worldwide Interoperability for Microwave Access(WiMAX), 5G new radio (NR) (e.g., using the NG-RAN 135 and 5GC 140),etc. The UE 105 may also support wireless communication using a WirelessLocal Area Network (WLAN) which may connect to other networks (e.g. theInternet) using a Digital Subscriber Line (DSL) or packet cable forexample. The use of one or more of these RATs may allow the UE 105 tocommunicate with an external client 130 (e.g. via elements of 5GC 140not shown in FIG. 1 , or possibly via a Gateway Mobile Location Center(GMLC) 125) and/or allow the external client 130 to receive locationinformation regarding the UE 105 (e.g., via the GMLC 125).

The UE 105 may include a single entity or may include multiple entitiessuch as in a personal area network where a user may employ audio, videoand/or data I/O devices and/or body sensors and a separate wireline orwireless modem. An estimate of a location of the UE 105 may be referredto as a location, location estimate, location fix, fix, position,position estimate or position fix, and may be geographic, thus providinglocation coordinates for the UE 105 (e.g., latitude and longitude) whichmay or may not include an altitude component (e.g., height above sealevel, height above or depth below ground level, floor level or basementlevel). Alternatively, a location of the UE 105 may be expressed as acivic location (e.g., as a postal address or the designation of somepoint or small area in a building such as a particular room or floor). Alocation of the UE 105 may also be expressed as an area or volume(defined either geographically or in civic form) within which the UE 105is expected to be located with some probability or confidence level(e.g., 67%, 95%, etc.) A location of the UE 105 may further be arelative location comprising, for example, a distance and direction orrelative X, Y (and Z) coordinates defined relative to some origin at aknown location which may be defined geographically, in civic terms, orby reference to a point, area, or volume indicated on a map, floor planor building plan. In the description contained herein, the use of theterm location may comprise any of these variants unless indicatedotherwise. When computing the location of a UE, it is common to solvefor local x, y, and possibly z coordinates and then, if needed, convertthe local coordinates into absolute ones (e.g. for latitude, longitudeand altitude above or below mean sea level).

Base stations (BSs) in the NG-RAN 135 shown in FIG. 1 include NR NodeBs, also referred to as gNBs, 110-1 and 110-2 (collectively andgenerically referred to herein as gNBs 110). Pairs of gNBs 110 in NG-RAN135 may be connected to one another—e.g. directly as shown in FIG. 1 orindirectly via other gNBs 110. Access to the 5G network is provided toUE 105 via wireless communication between the UE 105 and one or more ofthe gNBs 110, which may provide wireless communications access to the5GC on behalf of the UE 105 using 5G. In FIG. 1 , the serving gNB for UE105 is assumed to be gNB 110-1, although other gNBs (e.g. gNB 110-2) mayact as a serving gNB if UE 105 moves to another location or may act as asecondary gNB to provide additional throughout and bandwidth to UE 105.

Base stations (BSs) in the NG-RAN 135 shown in FIG. 1 may also include anext generation evolved Node B, also referred to as an ng-eNB, 114.Ng-eNB 114 may be connected to one or more gNBs 110 in NG-RAN 135—e.g.directly as shown in FIG. 1 or indirectly via other gNBs 110 and/orother ng-eNBs. An ng-eNB 114 may provide LTE wireless access and/orevolved LTE (eLTE) wireless access to UE 105. Some gNBs 110 (e.g. gNB110-2) and/or ng-eNB 114 in FIG. 1 may be configured to function aspositioning-only beacons which may transmit signals (e.g. directionalPRS) to assist positioning of UE 105 but may not receive signals from UE105 or from other UEs.

As noted, while FIG. 1 depicts nodes configured to communicate accordingto 5G communication protocols, nodes configured to communicate accordingto other communication protocols, such as, for example, an LTE protocolor IEEE 802.11x protocol, may be used. For example, in an Evolved PacketSystem (EPS) providing LTE wireless access to UE 105, a RAN may comprisean Evolved Universal Mobile Telecommunications System (UMTS) TerrestrialRadio Access Network (E-UTRAN) which may comprise base stationscomprising evolved Node Bs (eNBs). A core network for EPS may comprisean Evolved Packet Core (EPC). An EPS may then comprise an E-UTRAN plusEPC, where the E-UTRAN corresponds to NG-RAN 135 and the EPC correspondsto 5GC 140 in FIG. 1 . The methods and techniques described herein forsupport of UE 105 positioning using directional PRS may be applicable tosuch other networks—e.g. for directional PRS transmission from an eNBand/or from a WiFi IEEE 802.11 access point (AP).

The gNBs 110 and ng-eNB 114 can communicate with an Access and MobilityManagement Function (AMF) 115, which, for positioning functionality,communicates with a Location Management Function (LMF) 120. The AMF 115may support mobility of the UE 105, including cell change and handoverand may participate in supporting a signaling connection to the UE 105and possibly data and voice bearers for the UE 105. The LMF 120 maysupport positioning of the UE 105 when UE accesses the NG-RAN 135 andmay support position procedures/methods such as Assisted GNSS (A-GNSS),Observed Time Difference of Arrival (OTDOA), Real Time Kinematics (RTK),Precise Point Positioning (PPP), Differential GNSS (DGNSS), EnhancedCell ID (ECID), angle of arrival (AOA), angle of departure (AOD), and/orother position methods. The LMF 120 may also process location servicesrequests for the UE 105, e.g., received from the AMF 115 or from theGMLC 125. The LMF 120 may be connected to AMF 115 and/or to GMLC 125.The LMF 120 may be referred to by other names such as a Location Manager(LM), Location Function (LF), commercial LMF (CLMF) or value added LMF(VLMF). In some embodiments, a node/system that implements the LMF 120may additionally or alternatively implement other types oflocation-support modules, such as an Enhanced Serving Mobile LocationCenter (E-SMLC) or a Secure User Plane Location (SUPL) Location Platform(SLP). It is noted that in some embodiments, at least part of thepositioning functionality (including derivation of a UE 105's location)may be performed at the UE 105 (e.g., using signal measurements obtainedby UE 105 for signals transmitted by wireless nodes such as gNBs 110 andng-eNB 114, and assistance data provided to the UE 105, e.g. by LMF120).

The Gateway Mobile Location Center (GMLC) 125 may support a locationrequest for the UE 105 received from an external client 130 and mayforward such a location request to the AMF 115 for forwarding by the AMF115 to the LMF 120 or may forward the location request directly to theLMF 120. A location response from the LMF 120 (e.g. containing alocation estimate for the UE 105) may be similarly returned to the GMLC125 either directly or via the AMF 115 and the GMLC 125 may then returnthe location response (e.g., containing the location estimate) to theexternal client 130. The GMLC 125 is shown connected to both the AMF 115and LMF 120, though only one of these connections may be supported by5GC 140 in some implementations.

As further illustrated in FIG. 1 , the LMF 120 may communicate with thegNBs 110 and/or ng-eNB 114 using a New Radio Position Protocol A (whichmay be referred to as NPPa or NRPPa), which may be defined in 3GPPTechnical Specification (TS) 38.455. NRPPa may be the same as, similarto, or an extension of the LTE Positioning Protocol A (LPPa) defined in3GPP TS 36.455, with NRPPa messages being transferred between a gNB 110and the LMF 120, and/or between an ng-eNB 114 and the LMF 120, via theAMF 115. As further illustrated in FIG. 1 , LMF 120 and UE 105 maycommunicate using an LTE Positioning Protocol (LPP), which may bedefined in 3GPP TS 36.355. LMF 120 and UE 105 may also or insteadcommunicate using a New Radio Positioning Protocol (which may bereferred to as NPP or NRPP), which may be the same as, similar to, or anextension of LPP. Here, LPP and/or NPP messages may be transferredbetween the UE 105 and the LMF 120 via the AMF 115 and a serving gNB110-1 or serving ng-eNB 114 for UE 105. For example, LPP and/or NPPmessages may be transferred between the LMF 120 and the AMF 115 using a5G Location Services Application Protocol (LCS AP) and may betransferred between the AMF 115 and the UE 105 using a 5G Non-AccessStratum (NAS) protocol. The LPP and/or NPP protocol may be used tosupport positioning of UE 105 using UE assisted and/or UE based positionmethods such as A-GNSS, RTK, OTDOA and/or ECID. The NRPPa protocol maybe used to support positioning of UE 105 using network based positionmethods such as ECID (e.g. when used with measurements obtained by a gNB110 or ng-eNB 114) and/or may be used by LMF 120 to obtain locationrelated information from gNBs 110 and/or ng-eNBs 114, such as parametersdefining directional PRS transmission from gNBs 110 and/or ng-eNB 114.

With a UE assisted position method, UE 105 may obtain locationmeasurements and send the measurements to a location server (e.g. LMF120) for computation of a location estimate for UE 105. For example, thelocation measurements may include one or more of a Received SignalStrength Indication (RSSI), Round Trip signal propagation Time (RTT),Reference Signal Time Difference (RSTD), Reference Signal Received Power(RSRP) and/or Reference Signal Received Quality (RSRQ) for gNBs 110,ng-eNB 114 and/or a WLAN AP. The location measurements may also orinstead include measurements of GNSS pseudorange, code phase and/orcarrier phase for SVs 190. With a UE based position method, UE 105 mayobtain location measurements (e.g. which may be the same as or similarto location measurements for a UE assisted position method) and maycompute a location of UE 105 (e.g. with the help of assistance datareceived from a location server such as LMF 120 or broadcast by gNBs110, ng-eNB 114 or other base stations or APs). With a network basedposition method, one or more base stations (e.g. gNBs 110 and/or ng-eNB114) or APs may obtain location measurements (e.g. measurements of RSSI,RTT, RSRP, RSRQ or Time Of Arrival (TOA) for signals transmitted by UE105) and/or may receive measurements obtained by UE 105, and may sendthe measurements to a location server (e.g. LMF 120) for computation ofa location estimate for UE 105.

Information provided by the gNBs 110 and/or ng-eNB 114 to the LMF 120using NRPPa may include timing and configuration information fordirectional PRS transmission and location coordinates. The LMF 120 canthen provide some or all of this information to the UE 105 as assistancedata in an LPP and/or NPP message via the NG-RAN 135 and the 140.

An LPP or NPP message sent from the LMF 120 to the UE 105 may instructthe UE 105 to do any of a variety of things, depending on desiredfunctionality. For example, the LPP or NPP message could contain aninstruction for the UE 105 to obtain measurements for GNSS (or A-GNSS),WLAN, and/or OTDOA (or some other position method). In the case ofOTDOA, the LPP or NPP message may instruct the UE 105 to obtain one ormore measurements (e.g. RSTD measurements) of PRS signals and/ordirectional PRS signals transmitted within particular cells supported byparticular gNBs 110 and/or the ng-eNB 114 (or supported by some othertype of base station such as an eNB or WiFi AP). The UE 105 may send themeasurements back to the LMF 120 in an LPP or NPP message (e.g. inside aNAS message) via the serving gNB 110-1 (or serving ng-eNB 114) and theAMF 115.

As noted, while the communication system 100 is described in relation to5G technology, the communication system 100 may be implemented tosupport other communication technologies, such as GSM, WCDMA, LTE, etc.,that are used for supporting and interacting with mobile devices such asthe UE 105 (e.g., to implement voice, data, positioning, and otherfunctionalities). In some such embodiments, the 5GC 140 may beconfigured to control different air interfaces. For example, in someembodiments, 5GC 140 may be connected to a WLAN using a Non-3GPPInterWorking Function (N3IWF, not shown FIG. 1 ) in the 5GC 150. Forexample, the WLAN may support IEEE 802.11 WiFi access for UE 105 and maycomprise one or more WiFi APs. Here, the N3IWF may connect to the WLANand to other elements in the 5GC 150 such as AMF 115. In some otherembodiments, both the NG-RAN 135 and the 5GC 140 may be replaced byother RANs and other core networks. For example, in an EPS, the NG-RAN135 may be replaced by an E-UTRAN containing eNBs and the 5GC 140 may bereplaced by an EPC containing a Mobility Management Entity (MME) inplace of the AMF 115, an E-SMLC in place of the LMF 120 and a GMLC thatmay be similar to the GMLC 125. In such an EPS, the E-SMLC may use LPPain place of NRPPa to send and receive location information to and fromthe eNBs in the E-UTRAN and may use LPP to support positioning of UE105. In these other embodiments, positioning of a UE 105 usingdirectional PRSs may be supported in an analogous manner to thatdescribed herein for a 5G network with the difference that functions andprocedures described herein for gNBs 110, ng-eNB 114, AMF 115 and LMF120 may, in some cases, apply instead to other network elements sucheNBs, WiFi APs, an MME and an E-SMLC.

As noted, in some embodiments, positioning functionality may beimplemented, at least in part, using PRS transmissions and/ordirectional PRS transmissions, sent by base stations (such as the gNBs110 and/or ng-eNB 114) that are within range of the UE whose position isto be determined (e.g., the UE 105 of FIG. 1 ). The UE may, in someinstances, use the difference in the arrival times of downlink radiosignals (e.g., directional PRS transmissions) from a plurality of basestations (such as gNBs 110, ng-eNB 114, etc.) to compute the UE'sposition. For example, if a signal from one base station is received ata time t₁, and a signal from another base station is received at a timet₂, then the OTDOA or RSTD may be computed according to t₂-t₁.

FIG. 2 illustrates an example configuration 200 of directional PRStransmission (or PRS beamforming) at a base station 202 (represented bythe small solid circle) that supports three (3) cell sectors A (markedas sector 210), B (marked as sector 220), and C (marked as sector 230).The base station 202 may be similar to or the same as any of gNBs 110 orng-eNB 114 in FIG. 1 , or may be some other base station (e.g., an eNB)or WiFi AP. Each cell sector (also referred to herein as cell) has acoverage area that, in the example illustration of FIG. 2 , is a circlesector with a central angle of 120 degrees. In the example of FIG. 2 ,within each cell sector, six (6) separate directional PRS signals may bebroadcast over (approximately) non-overlapping circle sectors withcentral angles of 20 degrees each. Other sector configurations andapportionment for directional PRS signals, with beamwidth and beam shapecharacteristics that may be controlled based on the antennaconfiguration implemented for the base station 202, may be realized. Theseparate directional PRS signals in FIG. 2 are labelled An, Bn and Cnwhere, in this example, 1≤n>6. In order to distinguish the separatedirectional PRS signals An, Bn and Cn (e.g., so that a UE and/or alocation server can determine which directional PRS signal a UE ismeasuring) and/or to reduce interference, the directional PRS signalscan be made orthogonal in various ways as described previously, e.g., byassigning each directional PRS a different (or unique) vshift value, adifferent (or unique) PRS code sequence, a different (or unique) mutingpattern, a different (or unique) set of transmission times, or adifferent (or unique) combination of two or more of these signalcharacteristics.

The directional PRSs shown in FIG. 2 each span a continuous range ofhorizontal angles (or horizontal directions) within each circle sectorthat have a coverage of 20 degrees in a horizontal plane. Eachdirectional PRS shown in FIG. 2 may also span a continuous but limitedrange of vertical angles (or vertical directions), such as angles thatare angles of elevation ranging from zero degrees (which may coincidewith a horizontal direction) to 20 degrees (which may coincide with adirection elevated at 20 degrees to the horizontal). Further, there maybe other directional PRS signals, not shown in FIG. 2 , that may sharethe same ranges of horizontal angles shown in FIG. 2 but may havedifferent ranges of vertical angles. As an example, for each directionalPRS shown in FIG. 2 , there may be one directional PRS (shown in FIG. 2) with angles of elevation between zero and 20 degrees, anotherdirectional PRS (not shown in FIG. 2 ) with angles of elevation between20 and 40 degrees and a third directional PRS (not shown in FIG. 2 )with angles of elevation between 40 and 60 degrees, where each of thesedirectional PRSs has the same range of horizontal angles. In anotherexample, directional PRS signals may not be directional horizontally(e.g. may be transmitted throughout the coverage area of a particularcell) but may have different ranges of vertical angles. Control ofdirectional PRS signals transmitted by an antenna array for base station202 may be done by, for example, selecting individual antennas (orindividual antenna elements) of the base station's 202 antenna array totransmit signals, controlling relative phases and amplitudes of signalsdirected through the various selected antennas (or antenna elements) ofthe array, etc.

One convenient way to treat directional PRS signals Pn in any cellsector P (e.g., where P represents in FIG. 2 one of A, B or C) may be totreat each directional PRS signal as corresponding to a differenttransmitter or different cell, e.g., as if each directional PRS signalPn is transmitted by a different antenna such as an antenna associatedwith a distinct remote radio head for the cell sector P. A directionalPRS signal Pn could then be assigned a distinct PRS ID associated with adistinct PRS code sequence and/or a distinct vshift for the directionalPRS signal Pn. In some embodiments, a directional PRS signal could beassigned a distinct transmission point ID. For LTE access by a UE 105,this would allow a location server (e.g. an E-SMLC, SUPL SLP or LMF suchas LMF 120) to provide assistance data to the UE 105 for the directionalPRS signals Pn using existing capability in LPP. The assistance data canmake a UE 105 aware of the existence of the directional PRS signals andthe signal characteristics and other parameters for each directional PRSsignal (e.g., a PRS ID, transmission point ID, carrier frequency,bandwidth, position occasion periodicity and number of subframes, mutingpattern, expected RSTD measurement, etc.) and allow the UE 105 to makeRSTD measurements for OTDOA positioning. This support may not requireany changes to LPP (or NPP) since the location server could treat eachdirectional PRS Pn the same as a PRS transmitted by a distinct radiohead or distinct Distributed Antenna System (DAS) antenna for the cellsector P (as already supported in LPP).

In some embodiments, two or more different directional PRS signals Pnmay be transmitted at the same time by base station 202 but in a mannerthat allows any one PRS signal Pi to be distinguished from any other PRSsignal Pj by a UE 105 (e.g., by using a different frequency, differentfrequency shift or different PRS code sequence). In another embodiment,one PRS signal may be transmitted by base station 202 in a cell (e.g.cell A, B or C) in different directions at different non-overlappingtimes, using beamforming. For example, the base station 202 for the cellsector A in FIG. 2 may transmit a directional PRS signal usingbeamforming in a direction coinciding with directional PRS A1 for a timeinterval T1, may then change the direction of PRS signal transmission tocoincide with directional PRS A2 for a time interval T2, and maysubsequently change the direction of directional PRS signal transmissionto coincide with directional PRS signals A3, A4, A5 and A6 for timeintervals T3, T4, T5 and T6, respectively. If the time intervals T1, T2,. . . T6 are substantially non-overlapping, there may be no ambiguityregarding which directional PRS signal a UE 105 has measured if the timeinterval during which the directional PRS signal is measured can beobtained and compared with the known transmission intervals T1, T2, . .. Tn. Moreover, the order in which the angle of directional PRStransmission is changed in a cell may be varied, e.g., with the angle(of transmission, relative to some reference point or reference line)changed to correspond to any permutation of the different PRS signalsA1, A2, . . . A6. For example, in one embodiment, the base station 202may change the angle of directional PRS transmission in a cyclic manner(e.g. by transmitting directional PRS signals in the order A1, A2, . . .A6 or in the reverse order) and/or may rotate directional PRStransmission in a circle (e.g. by transmitting directional PRS signalsin the order A1, A2, . . . A6, followed by B1, B2, . . . B6 and then byC1, C2, . . . C6). A UE 105 that measures a PRS signal for the cellsector A may determine the time of measurement using timing informationincluded as party of the directional PRS signal or timing informationsent separately using another signal transmitted for the cell sector A(e.g. an omnidirectional cell-specific reference signal), or byobtaining the time using timing provided by a different cell S such asthe cell sector B or cell sector C in FIG. 2 or a serving cell for theUE 105 if different to cell sectors A, B and C. In the latter case, ifthe timing difference between cells A and S is known (e.g. due tosynchronizing transmission timing of cells A and S using GPS or GNSS ordetermining the transmission timing of cells A and S relative to GPS orGNSS), the measurement time for a directional PRS signal relative tocell S can be used to determine the measurement time relative to thecell sector A, and thus which directional PRS signal was measured.

There are several ways in which directional PRS signals may be utilizedfor location determination (e.g., to perform OTDOA positioning) for a UE105. In a first example, directional PRS signals may be used to obtaindirect information on the location of a UE 105. For example, if a UE 105is able to receive and measure directional PRS A5 in FIG. 2 , the UE 105is determined to be within the coverage area of directional PRS A5, andnot somewhere else in the coverage area of cell sector A. This may beused to improve the accuracy of UE location.

FIG. 3A shows a diagram 300 illustrating the use of directional(beamformed) PRS signals for location determination functionality. Inthis example, a UE 105 (not shown) measures or detects, for example, thedirectional PRS signal marked as PRS A5 in FIG. 2 . The UE 105 may alsomeasure/detect another directional PRS signal, namely, the directionalPRS D2, transmitted from another cell D with a different antennalocation to cell sector A. For example, cell D may be supported by a gNB110 (or ng-eNB 114) in FIG. 1 , which may be different to a gNB 110 thatsupports cell sector A. The UE 105 can then be inferred to be within theintersection region 310 of the two directional PRS beams as shown inFIG. 3A. The example in FIG. 3A may be referred to as positioning basedon an angle of departure (AOD) position method.

The location determination according to FIG. 3A may be performed at alocation-capable device that knows the locations of the base stationantennas for cells A and D and the precise directions of the directionalPRSs A5 and D2. For example, the location-capable device may be the basestation for cell A, the base station for cell D, the LMF 120 or the UE105 (e.g. if the UE 105 is provided with the locations of the basestation antennas for cells A and D and the precise directions of thedirectional PRSs by another entity such as a serving base station or theLMF 120).

FIG. 3B includes a diagram 320 showing another example implementation ofusing directional PRS signals to facilitate location determinationfunctionality. In the example of FIG. 3B a UE 105 (not shown)measures/detects the PRS A5 of FIG. 2 . Here the UE 105 and/or the gNB110 for cell A (or some other wireless node such as ng-eNB 114) measuresthe signal propagation time or round trip signal propagation time (RTT)between the UE 105 and the antenna for cell A. If the RTT has a measuredvalue of 2T plus or minus an uncertainty of U, the distance between theUE and the antenna for cell A would be given by (T c) with anuncertainty of (U c) where c is the speed of light, and assuming line ofsight (LOS) transmission. In this example, a determination may be made,based on the identity of the particular directional PRS detected by theUE 105, and the measured timing information (e.g., RTT), that the UE 105is located in a region 330 depicted in FIG. 3B. The example in FIG. 3Bmay be referred to as positioning based on Enhanced Cell ID (ECID).

The location determination according to FIG. 3B may be performed at alocation-capable device that knows the location of the base stationantenna for cell A, the precise direction of the directional PRS A5 andthe measured RTT and its uncertainty. For example, the location-capabledevice may be the base station for cell A, the LMF 120 or the UE 105(e.g. if the UE 105 is provided with the location of the base stationantenna for cell A, the precise direction of the directional PRS A5 andoptionally information to assist RTT determination, by another entitysuch as the base station for cell A).

In a further example implementation, directional (beamformed) PRS may beused to mitigate error/inaccurate positioning due to measurement ofmultipath signals. With multipath, a signal transmitted in a cell mayundergo reflection, refraction and/or scattering from one or moresurfaces, objects (e.g., walls and roofs of buildings) or materials(e.g. water, air) so that the signal received by a UE may not be a lineof sight (LOS) signal, but rather some redirection of a signaltransmitted from a source that may or may not be in the UE's LOS. Thiswill normally increase the signal propagation time to a UE compared toany LOS signal leading to errors in time-based position methods such asOTDOA.

FIG. 4 includes a diagram 400 illustrating two signals, namely, 51(marked as a signal 412) and S2 (marked as a signal 414), reaching a UE420 in a cell supported by a base station 410. The UE 420 may be similarto or the same as the UE 105 of FIG. 1 . The base station 410 may besimilar to or the same as any of the gNBs 110 or ng-eNB 114 of FIG. 1 ,or to some other base station, such as an eNB supporting LTEcommunication, or some other node or access point. In the exampledepicted in FIG. 4 , the signal S1 is a LOS signal directly receivedfrom the base station 410, while the signal S2 is a multipath signal,also referred to as a non-LOS (NLOS) signal, resulting from reflectionof a signal 416 that originated from the base station 410. Since themultipath (NLOS) signal S2 does not travel to the UE entirely along astraight line, it would typically initially travel from the cell antennain a different direction to the signal S1, as shown in FIG. 4 . Thus, ifthe cell is using directional PRSs, signals S1 and S2 would typicallycorrespond to different directional PRS signals (e.g., if the beamangles are narrow enough). For example, if the cell served by the basestation 410 corresponds to the cell A of FIG. 2 , and if signal S1corresponds to the directional PRS signal A3, signal S2 might correspondto another directional PRS such as A2 or A4. A location server (or theUE 420) that knows the approximate location of the UE 420 couldtherefore direct the UE 420 to measure signal S1 (e.g., directional PRSA3 in FIG. 2 ) but not direct the UE 420 to measure signal S2 (e.g.,directional PRS A2 or A4 in FIG. 2 ) by providing assistance data onlyfor signal S1. This would prevent or inhibit the UE 420 from measuring amultipath signal and improve the chance of measuring a LOS signal.Because different directional PRS signals may be associated, in someembodiments, with different (or unique) signal characteristics (e.g.,different PRS IDs, different frequency shifts (vshift), different PRScode sequences, different muting patterns, different transmission times,etc.), the UE 420 may thus be configured to measure a directional PRSsignal associated with some particular signal characteristic value(e.g., a particular PRS code sequence or a particular vshift value) orsome particular combination of signal characteristic values (e.g. aparticular PRS code sequence value and a particular vshift value) thatis/are associated with an expected LOS directional PRS signal (such assignal S1 412 in FIG. 4 or signal A3 in FIG. 2 ). However, UE 420 maynot be configured to measure (or may be configured to not measure) adirectional PRS signal that is not expected to be LOS (e.g. directionalPRS A2 or A4 in FIG. 2 ) that is associated with some other signalcharacteristic value or some other combination of signal characteristicvalues.

In another aspect, UE 105 may have multiple antennas (e.g. an antennaarray) that allow UE 105 to selectively receive and measure signals thatarrive from certain directions and to filter out and ignore signals thatarrive from other directions. A location server (e.g. LMF 120) mayprovide UE 105 with the direction of transmission for the LOS signal S1412 but may not provide information for the NLOS signal S2 414/416. UE105 may then use the multiple antennas (e.g. antenna array) to receiveand measure signals with the same direction of transmission as signal S1which may enable UE 105 to measure a TOA or RSTD (or other signalcharacteristic) for signal S1. The use of multiple antennas or anantenna array at UE 105 to tune reception to a particular direction oftransmission may reduce interference to signal S1 from other signals(such as signal S2) and may enable improved acquisition of signal S1 byUE 105 and higher measurement accuracy.

Directional (beamformed) PRS signals may also be used to mitigatemultipath effects in situations where a location server (or UE 420) maynot have the approximate location of the UE 420, or does not provideinformation to the UE 420 for only LOS signals. In this case, a locationserver (or the UE 420) may receive (or obtain) some measurements (e.g.OTDOA RSTD measurements) from the UE 420 for multipath signals (such asthe signal S2 414 in FIG. 4 ) as well as measurements (e.g. OTDOA RSTDmeasurements) for LOS signals (such as the signal S1 412 in FIG. 4 ).The location server (or UE 420) may obtain an initial position for theUE 420 using all of the measurements provided (or obtained) by the UE420. The location server (or UE 420) can then identify directional PRSsignals whose coverage areas do not include the determined location andtentatively identify these signals as multipath signals. The locationserver (or UE 420) can then re-determine the UE 420 location using onlymeasurements for signals not identified as multipath signals. Theprocess may be iterated by again identifying directional PRS signalswhose coverage areas do not include the new location and treating theseas multipath signals. Directional PRS signals initially tentativelyidentified as multipath signals may no longer need to be identified asmultipath signals if the new UE 420 location is now within theircoverage areas. Variants of this example procedure can also be used insituations in which the location determination procedure usesdirectional information as well as RSTD measurements to determine theinitial (and any subsequent) UE 420 location.

In another aspect, UE 420 may measure an angle of arrival (AOA) for adirectional PRS as well as other characteristics such as a TOA and/orRSTD. If the UE 420 measured AOA is consistent with (e.g. is equal to orapproximately equal to) the direction of transmission for the measureddirectional PRS, the UE 420 or a location-capable device such as anE-SMLC or LMF 120 may assume that the directional PRS measured by UE 420is LOS (e.g. such as being signal S1 412 in FIG. 4 ). Conversely, if theUE 420 measured AOA is not consistent with (e.g. is not equal to and notapproximately equal to) the direction of transmission for the measureddirectional PRS, the UE 420 or a location-capable device such as anE-SMLC or LMF 120 may assume that the directional PRS measured by UE 420is NLOS or multipath (e.g. such as being signal S2 414/416 in FIG. 4 ).

The above example embodiments, discussed (in part) in references toFIGS. 3A, 3B, and 4 , can be used to improve location determination fora UE 105 for UE assisted OTDOA, when, for example, the UE 105 providesmeasurements of directional PRSs to a location-capable device such as agNB 110, ng-eNB 114 or LMF 120 for determination of the location of UE105. The embodiments can also be used to improve location determinationfor UE based OTDOA for UE 105 when, for example, the network (e.g. a gNB110 or ng-eNB 114) or a location server (e.g. the LMF 120) provides theUE 105 with information on directional PRSs (e.g. directional PRStransmission directions and signal characteristics) as well as basestation coordinates and other PRS parameters. For example, for either UEassisted OTDOA or UE based OTDOA, a gNB 110 or an ng-eNB 114 in thecommunication system 100 of FIG. 1 could broadcast information fordirectional PRSs transmitted by this gNB 110 or ng-eNB 114 and possiblydirectional PRSs transmitted by other nearby gNBs 110 and/or ng-eNBs114.

FIG. 5 , and with further reference to FIG. 1 , shows a signaling flow500 that illustrates the various messages sent between components of acommunication network, such as the communication system 100 depicted inFIG. 1 , during a location session using LPP and/or NPP (also referredto as an LPP/NPP session) between the UE 105 and a location servercorresponding to the LMF 120. While the signaling flow 500 is discussed,for ease of illustration, in relation to a 5G communication networkimplementation, similar messaging may be realized for othercommunication technologies or protocols (such as EPS or WLAN).Furthermore, in some embodiments, the UE 105 itself may be configured todetermine its location using, for example, assistance data provided toit (e.g. by LMF 120 or by a serving gNB 110-1). The positioning protocolused for signaling flow 500 may be LPP, NPP or LPP combined with NPP(e.g. where an LPP message includes an embedded NPP message). Messagesfor the positioning protocol are accordingly referred to below asLPP/NPP messages to indicate that the messages are for LPP, NPP or LPPcombined with NPP. However, other positioning protocols are alsopossible such as the LPP Extensions (LPPe) protocol defined by the OpenMobile Alliance (OMA).

In some embodiments, a location session for UE 105 can be triggered whenthe LMF 120 receives a location request for UE 105 at action 501.Depending on the scenario, the location request may come to the LMF 120from the AMF 115 or from the GMLC 125 depicted in FIG. 1 . The LMF 120may then query the AMF 115 for information for the UE 105. The AMF 115may then send information for the UE 105 to the LMF 120 (not shown inFIG. 5 ). The information may indicate that UE 105 has 5G (or LTE oreLTE) wireless access (for the example embodiments of FIG. 5 ), and mayprovide a current 5G serving cell for UE 105 (e.g. a cell supported bygNB 110-1 which may be a serving gNB for UE 105) and/or may indicatethat the UE 105 supports location using LPP and/or NPP. Some or all ofthis information may have been obtained by the AMF 115 from UE 105and/or from the gNB 110-1, e.g., when the UE 105 attaches to andregisters with the 5GC 140.

To begin the LPP/NPP session (e.g., and based on an indication of UE 105support for LPP and/or NPP with 5G wireless access), the LMF 120 sendsan LPP/NPP Request Capabilities message at action 502 to the AMF 115serving the UE 105 (e.g. using 5G LCS AP). The AMF 115 may include theLPP/NPP Request Capabilities message within a 5G NAS transport message,at action 503, which is sent to the UE 105 (e.g., via a NAScommunication path in the NG-RAN 135, as illustrated in FIG. 1 ). The UE105 responds to the AMF 115 with an LPP/NPP Provide Capabilities messageat action 504, also within a 5G NAS transport message. The AMF 115extracts the LPP/NPP Provide Capabilities message from the 5G NAStransport message and relays the LPP/NPP Provide Capabilities message tothe LMF 120 (e.g., using 5G LCS AP) at action 505. Here, the LPP/NPPProvide Capabilities message sent at actions 504 and 505 may indicatethe positioning capabilities of the UE 105, e.g., the position methodsand associated assistance data supported by the UE 105 (such as A-GNSSpositioning, OTDOA positioning, ECID positioning, WLAN positioning,etc.) while accessing a 5G network. In the case of some position methods(e.g. OTDOA positioning), the capabilities may indicate if the UE 105 isable to measure, or able to improve measurement for, directional PRSsignals. For example, the capabilities may indicate that the UE 105 isable to tune PRS reception to a particular expected direction of arrivalfor a directional PRS using multiple antennas. However, in an aspect, aUE 105 may acquire and measure a directional PRS in the same way as anon-directional PRS (e.g. a PRS that is transmitted throughout an entirecell coverage area) and may not need to be aware of whether a PRS is adirectional PRS or non-directional PRS. In this aspect, the capabilitiesmay not indicate UE support for a directional PRS.

Based on the positioning capabilities of the UE 105 received at action505 and possibly based on the location request received at action 501(e.g. a location accuracy requirement included in the location requestreceived at action 501), the LMF 120 may select one or more positionmethods to locate UE 105 at action 506. For example, the LMF may selectOTDOA and/or ECID at action 506 in association with directional PRStransmitted from gNBs 110 and/or from ng-eNB 114.

Based on the position method(s) selected at action 506 and theassistance data indicated by the UE 105 as being supported at action505, the LMF 120 may determine assistance data for the UE 105 to supportthe selected position method(s). LMF 120 may then send an NRPPaInformation Request message at action 507, which may be relayed to theserving node gNB 110-1 by the AMF 115 (at action 508). The NRPPaInformation Request may request location related information for gNB110-1, such as the location of gNB 110-1, PRS configuration parametersfor gNB 110-1 and/or information concerning broadcast of assistance databy the gNB 110-1. The NRPPa Information Request sent at actions 507 and508 may include a request for configuration parameters related todirectional PRSs (e.g. a request for a direction of transmission, arange of horizontal angles, a range of vertical angles and/or othersignal characteristics for each directional PRS transmitted by gNB110-1). The serving node gNB 110-1 responds with an NRPPa InformationResponse message, at action 509, which may be relayed to the LMF 120 bythe AMF 115 at action 510. The NRPPa Information Response may providesome or all of the location related information requested at actions 507and 508. For example, when configuration parameters for PRSs and/ordirectional PRSs are requested at actions 507 and 508, the NRPPaInformation Response may provide signal characteristics and otherconfiguration information for each PRS and/or each directional PRSsupported by gNB 110-1. In the case of a directional PRS, the providedinformation may include a direction of transmission, a range ofhorizontal angles, a range of vertical angles and/or other signalcharacteristics (e.g. a carrier frequency, frequency shift (or vshift),bandwidth, code sequence, periodicity of positioning occasions, durationof a positioning occasion, and/or muting sequence). Actions 507-510 maybe repeated by the LMF 120 to obtain location related information (e.g.configuration parameters for directional PRSs) from other gNB 110 sand/or ng-eNBs nearby to UE 105, such as gNB 110-2 and ng-eNB 114 (notshown in FIG. 5 ).

In some implementations, serving gNB 110-1, and/or other gNBs 110 andng-eNBs such as gNB 110-2 and ng-eNB 114 (not shown in FIG. 5 ) maybroadcast assistance data to UE 105 (and to other UEs) at action 511and/or may provide assistance data to UE 105 by point to point means,e.g. using a Radio Resource Control Protocol (RRC) for 5G access (notshown in FIG. 5 ). The broadcast may use System Information Blocks(SIBs) for an RRC protocol in some implementations. The assistance datamay include configuration parameters and signal characteristics for PRSsignals and/or directional PRS signals that are transmitted by thesending gNB 110 and/or that are transmitted by other nearby gNBs 110and/or ng-eNB 114. The configuration parameters and signalcharacteristics for PRS signals and/or directional PRS signals broadcastby gNB 110-1 (and/or by other gNBs 110 and/or ng-eNB 114) may be thesame as the configuration parameters and signal characteristics for PRSsignals and/or directional PRS signals described further down for thelocation related information sent at actions 512 and 513. In someembodiments, actions 512 and 513, as described next, may not occur—e.g.if all location related information can be broadcast to UE by gNB 110-1and/or by other gNBs 110 and/or ng-eNB 114.

The LMF 120 may send some or all of the assistance data received ataction 510, and possibly other assistance data already known to the LMF120, to the UE 105 via an LPP/NPP Provide Assistance Data message sentto the AMF 115 at action 512, and relayed to the UE 105 by the AMF 115in a 5G NAS transport message at action 513. In the case of OTDOApositioning, the assistance data can include the identities of areference cell and neighbor cells supported by gNBs 110 and/or by ng-eNB114 and may include information for each cell, such as the cell carrierfrequency, and configuration parameters for each PRS transmitted withinthe cell. The assistance data may also include configuration parametersand signal characteristics that are associated with differentdirectional PRS signals that can be beamformed by the antenna arrays ofgNBs 110 and/or ng-eNB 114. For example, in such embodiments, theassistance data may include, for each directional PRS transmitted by thereference cell or a neighbor cell, such information as a PRS ID, atransmission point ID, a physical cell ID, a code sequence, a mutingpattern, a frequency shift (vshift), a periodicity and duration ofpositioning occasions etc. The information included in the assistancedata sent at actions 512 and 513 for each directional PRS may be thesame as information that can be included for a non-directional PRS, inwhich case the assistance data may not identify a directional PRS orprovide any distinct assistance data. However, in an aspect, theassistance data sent by LMF 120 at actions 512 and 513 may includedistinct information for a directional PRS, such as an identification ofa directional PRS, a direction of transmission, a range of horizontalangles and/or a range of vertical angles. In some implementations,information for directional PRSs such as that just described may be sentby LMF 120 at actions 512 and 513 when the position method(s) selectedat action 506 include(s) ECID, OTDOA, and/or other position methods(e.g. AOA, AOD, WLAN) that make use of directional PRS measurements byUE 105.

The NAS Transport message transmitted at the action 513 can be followedby an LPP/NPP Request Location Information message, again sent from theLMF 120 to AMF 115, at action 514, which is relayed to the UE 105 in a5G NAS transport message by AMF 115 at action 515. The LPP/NPP RequestLocation Information message may request one or more locationmeasurements from UE 105 and/or a location estimate according to, forexample, the position method(s) selected at action 506 and/or theposition capabilities of UE 105 sent to LMF 120 at actions 504 and 505.The positioning measurements may, for example, include TOA measurementsfor OTDOA or ECID, RSTD measurements for OTDOA, measurements of an AOA,RTT, RSRP, RSRQ and/or one way signal propagation delay for ECID, etc.Some of the positioning measurements may further be specified or allowedto be measured for directional PRSs—e.g. directional PRSs for whichconfiguration parameters and signal characteristics may have beenprovided, as previously described for actions 511, 512 and 513.

At action 516, the UE 105 can subsequently obtain some or all of thelocation measurements (and other information) requested at actions 514and 515. The location measurements may be made based, in part, on thedirectional PRSs transmitted by the serving gNB 110-1 and/or by othernearby gNBs 110 and/or ng-eNB 114. For example, for OTDOA, thedirectional PRSs may be transmitted by gNBs 110 and/or ng-eNB 114 withinthe reference cell and/or neighbor cells. The measurements obtained ataction 516 may comprise some or all of the measurements requested ataction 515 or implied at action 515 if action 515 requests a locationestimate from UE 105. UE 105 may measure a directional PRS (e.g. for thereference cell or a neighbor cell in the case of OTDOA or for a servingcell or neighbor cell in the case of ECID) based on configurationparameters and signal characteristics provided for the directional PRSin the location related information received at action 511 and/or ataction 513. For example, UE 105 may use one or more of a PRS ID, atransmission point ID, a physical cell ID, a code sequence, a mutingpattern, a frequency shift (vshift), a periodicity and duration ofpositioning occasions for a directional PRS to acquire the directionalPRS and measure characteristics such as a AOA, TOA, RSTD, RSSI, RSRP,RSRQ, RTT etc. In some aspects, UE 105 may also or instead use distinct(or unique) information for a directional PRS, if received at action 511and/or at action 513, to acquire and measure the directional PRS. Thedistinct (or unique) information may include an identification of adirectional PRS, a direction of transmission, a range of horizontalangles and/or a range of vertical angles. For example, as described inrelation to FIG. 4 , in some implementations, the UE 105 may selectivelymeasure directional PRSs that are expected to be LOS and ignoredirectional PRSs that are expected to be not received or to be NLOS (ormultipath). In addition, or instead, UE 105 may use multiple antennas oran antenna array to selectively receive and measure a directional PRSreceived for a particular direction of transmission and filter out andignore any signals including directional PRSs received for otherdirections of transmission.

In some embodiments, at least some of the location measurements obtainedat action 516 are provided in an LPP/NPP Provide Location Informationmessage, which is sent from the UE 105 to the AMF 115 in a 5G NAStransport message at action 517. The AMF 115 extracts the LPP/NPPProvide Location Information message from the 5G NAS transport message,and relays it to the LMF 120 (e.g., using 5G LCS AP) at action 518. Withthis information, the LMF 120 can then determine the UE 105 location ataction 519. The LMF 120 may employ one or more of the techniquesdescribed in association with FIGS. 3A, 3B and 4 to determine thelocation of UE 105. For example, when the location measurements returnedby UE 105 at actions 517 and 518 include measurements for one or moredirectional PRSs (e.g. measurements of TOA, RSRP, RSRQ, RSTD, RTT), theLMF 120 may identify a directional PRS for which a measurement wasprovided using a PRS ID or TP ID (e.g. which may be associated with aparticular code sequence and/or frequency shift (vshift)) or a time ofmeasurement (e.g. TOA measurement) and may then use one or more of thetechniques described for FIGS. 3A-4 such as ECID, AOA or OTDOA.

Following location determination at action 519, LMF 120 may send thedetermined location at action 520 to the entity (e.g. GMLC 125 or AMF115) which sent the location request at action 501.

In some embodiments, UE 105 may determine a location for UE 105following action 516 (not shown in FIG. 5 ). The location may bedetermined by UE 105 as just described for action 519 using techniquesdescribed in association with FIGS. 3A-4 . The location determination byUE 105 may be based on location related information received by UE 105at action 511 and/or at actions 512 and 513 including location relatedinformation described previously and other information such as thelocations of antennas for gNBs 110 and/or ng-eNB 114 and anytransmission timing differences for gNBs 110 and/or ng-eNB 114. UE 105may then return the determined location to LMF 120 at actions 517 and518 instead of returning location measurements. In this embodiment,action 519 may not occur.

FIG. 6 shows a structure of an example LTE subframe sequence 600 withPRS positioning occasions. Subframe sequence 600 may be applicable tobroadcast of PRS and directional PRS from ng-eNB 114 in communicationsystem 100. While FIG. 6 provides an example of a subframe sequence forLTE, similar subframe sequence implementations may be realized for othercommunication technologies/protocols, such as 5G and NR. For example, agNB 110 in communication system 100 may broadcast a PRS, a directionalPRS or other type of reference signal (RS) or directional RS (e.g. aTracking Reference Signal (TRS)) that is similar to subframe sequence600. In FIG. 6 , time is represented horizontally (e.g., on an X axis)with time increasing from left to right, while frequency is representedvertically (e.g., on a Y axis) with frequency increasing (or decreasing)from bottom to top. As shown in FIG. 6 , downlink and uplink LTE RadioFrames 610 may be of 10 ms duration each. For downlink FrequencyDivision Duplex (FDD) mode, Radio Frames 610 are organized, in theillustrated embodiments, into ten subframes 612 of 1 ms duration each.Each subframe 612 comprises two slots 614, each of, for example, 0.5 msduration.

In the frequency domain, the available bandwidth may be divided intouniformly spaced orthogonal subcarriers 616. For example, for a normallength cyclic prefix using, for example, 15 kHz spacing, subcarriers 616may be grouped into a group of twelve (12) subcarriers. Each grouping,which comprises the 12 subcarriers 616, is termed a resource block and,in the example above, the number of subcarriers in the resource blockmay be written as N_(SC) ^(RB)=12. For a given channel bandwidth, thenumber of available resource blocks on each channel 622, which is alsocalled the transmission bandwidth configuration 622, is indicated asN_(RB) ^(DL). For example, for a 3 MHz channel bandwidth in the aboveexample, the number of available resource blocks on each channel 622 isgiven by N_(RB) ^(DL)=15.

In the communication system 100 illustrated in FIG. 1 , an ng-eNB 114 ora gNB 110, such as either of the gNBs 110-1, or 110-2, may transmitframes, or other physical layer signaling sequences, supporting PRSsignals (i.e. a downlink (DL) PRS) according to frame configurationseither similar to, or (e.g. in the case of ng-eNB 114) the same as that,shown in FIG. 6 and (as described later) in FIG. 7 , which may bemeasured and used for UE (e.g., UE 105) position determination. Asnoted, other types of wireless nodes and base stations (e.g. an eNB orWiFi AP) may also be configured to transmit PRS signals configured in amanner similar to (or the same as) that depicted in FIGS. 6 and 7 .Since transmission of a PRS by a wireless node or base station isdirected to all UEs within radio range, a wireless node or base stationcan also be considered to transmit (or broadcast) a PRS. Further, insome implementations, a directional PRS, as described in relation toFIGS. 1-5 , may have a frame configuration similar to or the same asthat shown and described for FIGS. 6 and 7 .

A PRS, which has been defined in 3GPP LTE Release-9 and later releases,may be transmitted by wireless nodes (e.g. eNBs, ng-eNB 114) afterappropriate configuration (e.g., by an Operations and Maintenance (O&M)server). A PRS may be transmitted in special positioning subframes thatare grouped into positioning occasions. For example, in LTE, a PRSpositioning occasion can comprise a number N_(PRS) of consecutivepositioning subframes where the number N_(PRS) may be between 1 and 160(e.g. may include the values 1, 2, 4 and 6 as well as other values). ThePRS positioning occasions for a cell supported by a wireless node mayoccur periodically at intervals, denoted by a number T_(PRS), ofmillisecond (or subframe) intervals where T_(PRS) may equal 5, 10, 20,40, 80, 160, 320, 640, or 1280 (or any other appropriate value). As anexample, FIG. 6 illustrates a periodicity of positioning occasions whereN_(PRS) equals 4 618 and T_(PRS) is greater than or equal to 20 620. Insome embodiments, T_(PRS) may be measured in terms of the number ofsubframes between the start of consecutive positioning occasions.

Within each positioning occasion, a PRS may be transmitted with aconstant power. A PRS can also be transmitted with zero power (i.e.,muted). Muting, which turns off a regularly scheduled PRS transmission,may be useful when PRS signals between different cells overlap byoccurring at the same or almost the same time. In this case, the PRSsignals from some cells may be muted while PRS signals from other cellsare transmitted (e.g. at a constant power). Muting may aid signalacquisition and TOA and RSTD measurement, by UEs (such as the UE 105depicted in FIGS. 1 and 5 and the UE 420 in FIG. 4 ), of PRS signalsthat are not muted (by avoiding interference from PRS signals that havebeen muted). Muting may be viewed as the non-transmission of a PRS for agiven positioning occasion for a particular cell. Muting patterns (alsoreferred to as muting sequences) may be signaled (e.g. using LPP or NPP)to a UE using bit strings. For example, in a bit string signaled toindicate a muting pattern, if a bit at position j is set to ‘0’, thenthe UE may infer that the PRS is muted for a j^(th) positioningoccasion.

To further improve hearability of PRS, positioning subframes may below-interference subframes that are transmitted without user datachannels. As a result, in ideally synchronized networks, PRSs mayreceive interference from other cell PRSs with the same PRS patternindex (i.e., with the same frequency shift), but not from datatransmissions. The frequency shift, in LTE, for example, is defined as afunction of a PRS ID for a cell or TP (denoted as N_(ID) ^(PRS)) or as afunction of a Physical Cell Identifier (PCI) (denoted as N_(ID) ^(cell))if no PRS ID is assigned, which results in an effective frequency re-usefactor of 6.

To also improve hearability of a PRS (e.g., when PRS bandwidth islimited such as with only 6 resource blocks corresponding to 1.4 MHzbandwidth), the frequency band for consecutive PRS positioning occasions(or consecutive PRS subframes) may be changed in a known and predictablemanner via frequency hopping. In addition, a cell supported by awireless node may support more than one PRS configuration, where eachPRS configuration may comprise a distinct frequency offset (vshift), adistinct carrier frequency, a distinct bandwidth, a distinct codesequence, and/or a distinct sequence of PRS positioning occasions with aparticular number of subframes (N_(PRS)) per positioning occasion and aparticular periodicity (T_(PRS)). In some implementation, one or more ofthe PRS configurations supported in a cell may be for a directional PRSand may then have additional distinct characteristics such as a distinctdirection of transmission, a distinct range of horizontal angles and/ora distinct range of vertical angles. Further enhancements of a PRS mayalso be supported by a wireless node.

As discussed herein (e.g. for actions 511, 512 and 513 of signaling flow500), in some embodiments, OTDOA assistance data may be provided to a UE105 by a location server (e.g., the LMF 120 of FIG. 1 , an E-SMLC, etc.)for a “reference cell” and one or more “neighbor cells” or “neighboringcells” relative to the “reference cell.” For example, the assistancedata may provide the center channel frequency of each cell, various PRSconfiguration parameters (e.g., N_(PRS), T_(PRS), muting sequence,frequency hopping sequence, PRS ID, PRS bandwidth), a cell global ID,PRS signal characteristics associated with a directional PRS, and/orother cell related parameters applicable to OTDOA or some other positionmethod (e.g. ECID).

PRS-based positioning by a UE 105 may be facilitated by indicating theserving cell for the UE 105 in the OTDOA assistance data (e.g. with thereference cell indicated as being the serving cell). In the case of a UE105 with 5G wireless access, the reference cell may be chosen by the LMF120 as some cell (e.g. supported by a gNB 110) with good coverage at theexpected approximate location of the UE 105 (e.g., as indicated by theknown 5G serving cell for the UE 105).

In some embodiments, OTDOA assistance data may also include “expectedRSTD” parameters, which provide the UE 105 with information about theRSTD values the UE 105 is expected to measure at its current locationbetween the reference cell and each neighbor cell, together with anuncertainty of the expected RSTD parameter. The expected RSTD, togetherwith the associated uncertainty, may define a search window for the UE105 within which the UE 105 is expected to measure the RSTD value. OTDOAassistance information may also include PRS configuration informationparameters, which allow a UE 105 to determine when a PRS positioningoccasion occurs on signals received from various neighbor cells relativeto PRS positioning occasions for the reference cell, and to determinethe PRS sequence transmitted from various cells in order to measure asignal Time of Arrival (TOA) or RSTD.

Using the RSTD measurements, the known absolute or relative transmissiontiming of each cell, and the known position(s) of wireless node physicaltransmitting antennas for the reference and neighboring cells, the UE105's position may be calculated (e.g., by the UE 105, by the LMF 120,or by some other node such as a gNB 110 or ng-eNB 114). Moreparticularly, the RSTD for a neighbor cell “k” relative to a referencecell “Ref”, may be given as (TOA_(k)−TOA_(Ref)), where the TOA valuesmay be measured modulo one subframe duration (1 ms) to remove theeffects of measuring different subframes at different times. TOAmeasurements for different cells may then be converted to RSTDmeasurements (e.g. as defined in 3GPP TS 36.214 entitled “Physicallayer; Measurements”) and sent to the location server (e.g., the LMF 120or an E-SMLC) by the UE 105. Using (i) the RSTD measurements, (ii) theknown absolute or relative transmission timing of each cell, (iii) theknown position(s) of physical transmitting antennas for the referenceand neighboring cells, and/or (iv) directional PRS characteristics suchas a direction of transmission, the UE 105's position may be determined.

FIG. 7 illustrates further aspects of PRS transmission for a cellsupported by a wireless node (such as an ng-eNB 114 or a gNB 110).Again, PRS transmission for LTE is assumed in FIG. 7 although the sameor similar aspects of PRS transmission to those shown in and describedfor FIG. 7 may apply to 5G, NR and/or other wireless technologies. FIG.7 shows how PRS positioning occasions are determined by a System FrameNumber (SFN), a cell specific subframe offset (Δ_(PRS))) and the PRSPeriodicity (T_(PRS)) 720. Typically, the cell specific PRS subframeconfiguration is defined by a “PRS Configuration Index” I_(PRS) includedin the OTDOA assistance data. The PRS Periodicity (T_(PRS)) 720 and thecell specific subframe offset (Δ_(PRS)) are defined based on the PRSConfiguration Index I_(PRS), in 3GPP TS 36.211 entitled “Physicalchannels and modulation,” as illustrated in Table 1 below.

TABLE 1 PRS configuration PRS periodicity T_(PRS) PRS subframe offsetIndex I_(PRS) (subframes) Δ_(PRS) (subframes) 0-159 160 I_(PRS) 160-479320 I_(PRS)-160 480-1119 640 I_(PRS)-480 1120-2399 1280 I_(PRS)-11202400-2404 5 I_(PRS)-2400 2405-2414 10 I_(PRS)-2405 2415-2434 20I_(PRS)-2415 2435-2474 40 I_(PRS)-2435 2475-2554 80 I_(PRS)-24752555-4095 Reserved

A PRS configuration is defined with reference to the System Frame Number(SFN) of a cell that transmits PRS. PRS instances, for the firstsubframe of the N_(PRS) downlink subframes comprising a first PRSpositioning occasion, may satisfy:

(10×n _(ƒ) +[n _(s)/2]−Δ_(PRS))mod T _(PRS)=0  (1)

where n_(ƒ) is the SFN with 0≤n_(ƒf)≤1023, n_(s) is the slot numberwithin the radio frame defined by n_(ƒ) with 0≤n_(s)≤19, T_(PRS) is thePRS periodicity, and Δ_(PRS) is the cell-specific subframe offset.

As shown in FIG. 7 , the cell specific subframe offset Δ_(PRS) 752 maybe defined in terms of the number of subframes transmitted starting fromSystem Frame Number 0 (Slot ‘Number 0’, marked as slot 750) to the startof the first (subsequent) PRS positioning occasion. In FIG. 7 , thenumber of consecutive positioning subframes 718 (N_(PRS)) equals 4.

In some embodiments, when a UE 105 receives a PRS configuration indexI_(PRS) in the OTDOA assistance data for a particular cell, the UE 105may determine the PRS periodicity T_(PRS) and PRS subframe offsetΔ_(PRS) using Table 1. The UE 105 may then determine the radio frame,subframe and slot when a PRS is scheduled in the cell (e.g., usingequation (1)). The OTDOA assistance data may be determined by, forexample, the LMF 120 or an E-SMLC and includes assistance data for areference cell, and a number of neighbor cells supported by variouswireless nodes.

Typically, PRS occasions from all cells in a network that use the samefrequency are aligned in time and may have a fixed known time offsetrelative to other cells in the network that use a different frequency.In SFN-synchronous networks all wireless nodes (e.g. gNBs, ng-eNBs,eNBs, etc.) may be aligned on both frame boundary and system framenumber. Therefore, in SFN-synchronous networks all cells supported bythe various wireless nodes may use the same PRS configuration index forany particular frequency of PRS transmission. On the other hand, inSFN-asynchronous networks, the various wireless nodes may be aligned ona frame boundary, but not system frame number. Thus, in SFN-asynchronousnetworks the PRS configuration index for each cell may be configuredseparately by the network so that PRS occasions align in time.

A UE 105 may determine the timing of the PRS occasions (e.g., in an LTEnetwork or a 5G network such as that in communication system 100) of thereference and neighbor cells for OTDOA positioning, if the UE 105 canobtain the cell timing (e.g., SFN or Frame Number) of at least one ofthe cells, e.g., the reference cell or a serving cell (e.g. which may beperformed as part of action 516 in FIG. 5 ). The timing of the othercells may then be derived by the UE 105 based, for example, on theassumption that PRS occasions from different cells overlap.

As defined by 3GPP (e.g., in 3GPP TS 36.211), for LTE systems, thesequence of subframes used to transmit PRS (e.g., for OTDOA positioning)may be characterized and defined by a number of parameters, as describedpreviously, comprising: (i) a reserved block of bandwidth (BW), (ii) theconfiguration index I_(PRS), (iii) the duration N_(PRS), (iv) anoptional muting pattern; and (v) a muting sequence periodicity T_(REP)which can be implicitly included as part of the muting pattern in (iv)when present. In some cases, with a fairly low PRS duty cycle,N_(PRS)=1, T_(PRS)=160 subframes (equivalent to 160 ms), and BW=1.4, 3,5, 10, 15 or 20 MHz. To increase the PRS duty cycle, the N_(PRS) valuecan be increased to six (i.e., N_(PRS)=6) and the bandwidth (BW) valuecan be increased to the system bandwidth (i.e., BW=LTE system bandwidthin the case of LTE). An expanded PRS with a larger N_(PRS) (e.g.,greater than six) and/or a shorter T_(PRS) (e.g., less than 160 ms), upto the full duty cycle (i.e., N_(PRS)=T_(PRS)), may also be used inlater versions of LPP according to 3GPP TS 36.355. A directional PRS(e.g. as described in association with FIGS. 1-5 ) may be configured asjust described according to 3GPP TSs and may, for example, use a low PRSduty cycle (e.g. N_(PRS)=1, T_(PRS)=160 subframes) or a high duty cycle.

FIG. 8 shows a flowchart of an example procedure 800, performed at afirst base station, configured to transmit signaling (e.g., according toLTE, NR or 5G protocols), to support and facilitate positioning of amobile device (e.g. the UE 105 or UE 420). The procedure 800 may beperformed by a base station such as the base station 410 in FIG. 4 , thebase station 202 in FIG. 2 , an eNB for LTE, a gNB for 5G or NR such asa gNB 110 in FIG. 1 , or an ng-eNB for 5G such as ng-eNB 114 in FIG. 1 .The procedure 800 may also be supported by a positioning only beaconthat transmits signals (e.g. NR or LTE signals) but does not receivesignals.

The procedure 800 includes generating at block 810 (by the first basestation) a plurality of directional positioning reference signals (PRSs)for at least one cell for the first base station, with each of theplurality of directional PRSs comprising at least one signalcharacteristic and a direction of transmission. The at least one cellmay be a serving cell for the mobile device. In an embodiment, at leastone of the at least one signal characteristic and the direction oftransmission may be unique (e.g. may be different to a corresponding atleast one signal characteristic and/or a corresponding direction oftransmission, respectively, for any other directional PRS transmittedfor the at least one cell, by the first base station or by other nearbybase stations).

The procedure 800 further includes transmitting at block 820 each of theplurality of directional PRSs within the at least one cell, wherein eachof the plurality of directional PRSs is transmitted in the direction oftransmission. The at least one signal characteristic for any directionalPRS in the plurality of directional PRSs may indicate the direction oftransmission for that directional PRS. For example, the at least onesignal characteristic may identify the directional PRS, and may therebyindicate a known direction of transmission for this directional PRS, dueto being different to a corresponding at least one signal characteristicfor any other directional PRS in the plurality of directional PRSs.Thus, the at least one signal characteristic may be used to reduce orremove, for example, multipath interference, or to otherwise facilitatelocation determination for the mobile device as described in relation toFIGS. 3A-4 .

The at least one signal characteristic may comprise, for example, afrequency (e.g. a carrier frequency), a frequency shift, a codesequence, a muting pattern, a transmission time or set of transmissiontimes, or some combination of these. In some embodiments, transmittingthe plurality of directional PRSs at block 820 may include directing theplurality of directional PRSs through a controllable antenna array (ofthe base station) configured to beamform each directional PRS in therespective direction of transmission. In some embodiments, the directionof transmission (for a particular directional PRS) may include a firstangle from a continuous range of horizontal angles, and/or a secondangle from a continuous range of vertical angles. In some embodiments,the direction of transmission for a particular directional PRS maycomprise a continuous range of horizontal angles, a continuous range ofvertical angles, or a combination thereof. In some embodiments, thedirection of transmission for a particular directional PRS may beselected from a set of discrete directions of transmission (e.g.,represented as an angle or a plurality of angles). The directional PRSsmay be transmitted in substantially non-overlapping directions that areeach associated with the at least one signal characteristic that allowsidentification of each directional PRS (and thus allows determination ofthe direction of transmission for each directional PRS).

In some embodiments, at least one of the plurality of directional PRSstransmitted at block 820 may be detectable by the mobile device tofacilitate location determination of the mobile device at alocation-capable device based on an observed time difference of arrival(OTDOA) position method, an angle of departure (AOD) position method,and/or an Enhanced Cell ID (ECID) position method. Other positionmethods that utilize the transmitted directional PRS signals may also beused. As noted, a location determination operation at a location-capabledevice may be performed at one or more of, for example, the first basestation (transmitting the directional PRS), a second base stationdifferent to the first base station, the mobile device, a locationserver (e.g., an LMF 120, an SLP or an E-SMLC), and/or other types ofdevices. In these embodiments, the first base station may send thedirection of transmission for the at least one of the plurality ofdirectional PRSs and/or other configuration parameters and signalscharacteristics for the at least one of the plurality of directionalPRSs to the location-capable device—e.g. as at actions 509 and 510 insignaling flow 500 when LMF 120 is the location-capable device or as ataction 511 when UE 105 is the location-capable device.

In embodiments where at least one of the plurality of directional PRSstransmitted at block 820 is detectable by the mobile device tofacilitate location determination of the mobile device at alocation-capable device, the at least one of the plurality ofdirectional PRSs may be detectable by the mobile device based on thedirection of transmission for the at least one of the plurality ofdirectional PRSs, the at least one signal characteristic for the atleast one of the plurality of directional PRSs, or a combinationthereof. For example, the at least one signal characteristic for the atleast one of the plurality of directional PRSs may be used by the mobiledevice to acquire and measure the at least one of the plurality ofdirectional PRSs. For example, the mobile device may integrate thedirectional PRS signal using coherent or non-coherent integration over aperiod of time such as the duration of one positioning occasion and maycompare or correlate the integrated signal with an expected signal thathas the same at least one signal characteristic, which may enable themobile device to detect and measure the directional PRS. In some ofthese embodiments, the at least one signal characteristic may comprise asingle signal characteristic that is different from a correspondingsingle signal characteristic for other PRS and/or other directional PRSsignals that may be received by the mobile device. Alternatively, insome of these embodiments, the at least one signal characteristic maycomprise a combination of two or more signal characteristics that arecollectively different from a corresponding combination of two or moresignal characteristics for other PRS and/or other directional PRSsignals that may be received by the mobile device. In some of theseembodiments, the mobile device may use the direction of transmission forthe at least one of the plurality of directional PRSs detectable by themobile device to detect this directional PRS by using multiple antennasor an antenna array to selectively receive only signals transmitted inthe direction of transmission for this directional PRS as described inassociation with FIG. 4 .

In some embodiments, the procedure 800 may further comprise sending atleast one of the direction of transmission or the at least one signalcharacteristic for at least one of the plurality of directional PRSs tothe mobile device. The sending may be based on broadcast within the atleast one cell or on point to point transfer—e.g. as described foraction 511 in signaling flow 500 in the case of broadcast.

In embodiments where at least one of the plurality of directional PRSstransmitted at block 820 is detectable by the mobile device tofacilitate location determination of the mobile device at alocation-capable device, the location determination operation at thelocation-capable device may include determining a presence or absence ofmultipath for the at least one of the plurality of directional PRSsbased on the associated direction of transmission for the at least oneof the plurality of directional PRSs and an approximate location for themobile device. Here, determining the location of the mobile device atthe location-capable device may be based, at least in part, on thedetermined presence or absence of multipath. For example, and adescribed for FIG. 4 , when a presence of multipath is determined,determining the location of the mobile device may include disregarding(e.g. ignoring) the at least one of the plurality of directional PRSstransmitted at block 820. Conversely, and as also described for FIG. 4 ,when an absence of multipath is determined, determining the location ofthe mobile device may include using the at least one of the plurality ofdirectional PRSs transmitted at block 820 (e.g. using a measurementobtained by the mobile device for the at least one of the plurality ofdirectional PRSs). The approximate location for the mobile device may bebased, at least in part, on a serving cell for the mobile device or on aprevious determination of the location of the mobile device. Forexample, the previous determination may be based, at least in part, onthe at least one of the plurality of directional PRSs transmitted atblock 820 and detectable by the mobile device (e.g. based on ameasurement obtained by the mobile device for the at least one of theplurality of directional PRSs).

FIG. 9 shows a flowchart of an example procedure 900, generallyperformed at a mobile device (e.g., a UE such as the UE 105 in FIGS. 1and 5 or the UE 420 in FIG. 4 ), for supporting positioning of themobile device. The procedure 900 includes receiving at block 910, at themobile device, a first directional positioning reference signal (PRS)transmitted by a first base station (e.g. a gNB 110, an ng-eNB 114 or aneNB) within at least one cell for the first base station, with the firstdirectional PRS comprising at least one first signal characteristic anda first direction of transmission. The at least one cell may be aserving cell for the mobile device—e.g. if the first base station is gNB110-1 in FIG. 1 and the mobile device is UE 105. As noted, the at leastone first signal characteristic may include one or more of, for example,a carrier frequency, a frequency shift (e.g. a vshift), a code sequence(e.g. a PRS code sequence), a muting pattern, a bandwidth, and/or atransmission time (or a set of transmission times). In some embodiments,the first directional PRS is transmitted from the first base stationthrough a controllable antenna array configured to beamform the firstdirectional PRS in the first direction of transmission. As also noted,the first direction of transmission may include (or be defined) by adirection with a continuous range of horizontal angles, and/or acontinuous range of vertical angles.

With continued reference to FIG. 9 , the procedure 900 further includesobtaining at block 920 at least one first measurement for the firstdirectional PRS based, at least in part, on the at least one firstsignal characteristic. Block 920 may correspond to action 516 or part ofaction 516 in signaling flow 500. The at least one first measurement forthe first directional PRS obtained at block 920 may include, forexample, a Time Of Arrival (TOA), a Reference Signal Time Difference(RSTD), a Received Signal Strength Indication (RSSI), a Reference SignalReceived Power (RSRP), a Reference Signal Received Quality (RSRQ), anAngle of Arrival (AOA), a signal propagation time, a round trip signalpropagation time (RTT), a detection of the at least one first signalcharacteristic, and/or any combination of these. The at least one firstsignal characteristic for the first directional PRS may be used by themobile device to acquire and measure the first directional PRS signal atblock 920. For example, the mobile device may integrate the firstdirectional PRS and other received signals using coherent ornon-coherent integration over a period of time such as the duration ofone PRS positioning occasion and may compare or correlate the integratedsignal with an expected signal that has the same at least one firstsignal characteristic, which may enable the mobile device to detect andmeasure the first directional PRS. In some embodiments, the at least onefirst signal characteristic may comprise a single signal characteristicthat is different from a corresponding single signal characteristic forother PRS and/or other directional PRS signals that may also be receivedby the mobile device. In other embodiments, the at least one firstsignal characteristic may comprise a combination of two or more signalcharacteristics that are collectively different from a correspondingcombination of two or more signal characteristics for other PRS and/orother directional PRS signals that may be received by the mobile device.In some embodiments, the mobile device may use the first direction oftransmission for the first directional PRS to acquire and measure thefirst directional PRS at block 920 by using multiple antennas or anantenna array to selectively receive only signals transmitted in thefirst direction of transmission as described in association with FIG. 4. In some embodiments, the at least one first signal characteristic forthe first directional PRS may be received by the mobile device (e.g.prior to performing block 920) from the first base station (e.g. asdescribed for action 511 of signaling flow 500) or from a locationserver such as an E-SMLC, SLP or LMF 120 (e.g. as described for actions512 and 513 of signaling flow 500).

The procedure 900 further includes facilitating at block 930 locationdetermination of the mobile device at a location-capable device based,at least in part, on the at least one first measurement. The locationdetermination for block 930 may correspond to action 519 in signalingflow 500. As discussed herein, the location-capable device, where atleast some of the location determination operations may be performed,may include one or more of, for example, the mobile device, the firstbase station, some other base station, and/or a location server (e.g.the LMF 120 of FIG. 1 , an E-SMLC, an SLP, etc.) The locationdetermination of the mobile device at the location-capable device may bebased on, for example, an observed time difference of arrival (OTDOA)position method, an angle of departure (AOD) position method, anEnhanced Cell ID (ECID) position method, or on some combination ofthese, and may employ one or more of the techniques described herein inassociation with FIGS. 3A, 3B and 4 . When the location-capable devicecorresponds to the first base station or a location server (e.g. anE-SMLC, SLP or LMF 120), facilitating the location determination inblock 930 may include sending the at least one first measurement for thefirst directional PRS to the location-capable device—e.g. as at actions517 and 518 in signaling flow 500 when the location-capable device isLMF 120.

In some embodiments, location determination of the mobile device at thelocation-capable device may include determining a presence or absence ofmultipath for the first directional PRS based on the first direction oftransmission for the first directional PRS and an approximate locationfor the mobile device. Here, determining the location of the mobiledevice may be based, at least in part, on the determined presence orabsence of multipath. For example, and as described for FIG. 4 , when apresence of multipath is determined, determining the location of themobile device may include disregarding (e.g. ignoring) the at least onefirst measurement obtained at block 920. Conversely, and as alsodescribed for FIG. 4 , when an absence of multipath is determined,determining the location of the mobile device may include using the atleast one first measurement obtained at block 920 in the locationdetermination. The approximate location for the mobile device may bebased, at least in part, on a serving cell for the mobile device or on aprevious determination of the location of the mobile device based, atleast in part, on the at least one first measurement.

In some embodiments, location determination of the mobile device may beimplemented based on measurements by the mobile device of multipledirectional PRS signals. Thus, in such embodiments, the procedure 900may further include receiving, at the mobile device, a seconddirectional PRS transmitted by a second base station within at least onecell for the second base station, with the second directional PRSincluding at least one second signal characteristic and a seconddirection of transmission, and with the at least one second signalcharacteristic and the second direction of transmission for the seconddirectional PRS being, respectively, different from the at least onefirst signal characteristic and the first direction of transmission forthe first directional PRS. The procedure 900, in such embodiments, mayalso include obtaining at least one second measurement for the seconddirectional PRS based, at least in part, on the at least one secondsignal characteristic for the second directional PRS, and facilitatinglocation determination of the mobile device at the location-capabledevice based, at least in part, on the at least one first measurementand the at least one second measurement.

In some embodiments of the procedure 900, at least one of the at leastone first signal characteristic and the first direction of transmissionmay be unique (e.g. may be different to a corresponding signalcharacteristic and/or corresponding direction of transmission,respectively, for any other directional PRS transmitted within the atleast one cell, by the first base station or by some other nearby basestation).

FIG. 10 shows a flowchart of an example procedure 1000, generallyperformed at a location-capable device for supporting positioning of amobile device such as the UE 105 of FIGS. 1 and 5 or the UE 420 of FIG.4 . The procedure 1000 may be performed by the mobile device, by a basestation such as an eNB, ng-eNB 114 or a gNB 110, or by a location serversuch as an E-SMLC, SLP or the LMF 120.

The procedure 1000 includes obtaining at block 1010 at least one firstmeasurement from the mobile device for a first directional positioningreference signal (PRS) transmitted by a first base station in at leastone cell for the first base station, where the first directional PRScomprises at least one first signal characteristic and a first directionof transmission. The at least one cell may be a serving cell for themobile device—e.g. if the first base station corresponds to gNB 110-1and the mobile device corresponds to UE 105. The at least one firstmeasurement may be obtained at block 1010 directly if thelocation-capable device is the mobile device, or may be obtained atblock 1010 by being received at the location-capable device from themobile device if the location-capable device is a base station (e.g. thefirst base station) or a location server (e.g. the LMF 120). Forexample, the at least one first measurement may be received from themobile device in an Radio Resource Control (RRC) message if thelocation-capable device is a base station or may be received from themobile device in an LPP, NPP or NRPP message if the location-capabledevice is a location server (e.g. as described for actions 517 and 518for signaling flow 500 for a location server corresponding to LMF 120).

The procedure 1000 further includes determining at block 1020 a locationof the mobile device based, at least in part, on the at least one firstmeasurement and the first direction of transmission. In some embodimentswhere the location-capable device is a location server (e.g. LMF 120),block 1020 may correspond to action 519 in signaling flow 500.

As discussed herein, the at least one first signal characteristic maycomprise a carrier frequency, a frequency shift (e.g. a vshift), a codesequence (e.g. a PRS code sequence), a muting pattern, a bandwidth, atransmission time (or a set of transmission times), or some combinationof these. The first direction of transmission may include a continuousrange of horizontal angles, and/or a continuous range of verticalangles. In some embodiments, the first directional PRS may betransmitted from the first base station through a controllable antennaarray configured to beamform the first directional PRS in the firstdirection of transmission. The at least one first measurement for thefirst directional PRS may include a Time Of Arrival (TOA), a ReferenceSignal Time Difference (RSTD), a Received Signal Strength Indication(RSSI), a Reference Signal Received Power (RSRP), a Reference SignalReceived Quality (RSRQ), an Angle of Arrival (AOA), a signal propagationtime, a round trip signal propagation time (RTT), a detection of the atleast one first signal characteristic, and/or some combination of these.

In some embodiments, the location-capable device may include the mobiledevice, and the procedure 1000 may further include, in such embodiments,receiving the at least one first signal characteristic and/or the firstdirection of transmission from the first base station or from a locationserver such as an E-SMLC, SLP or an LMF (e.g. LMF 120). The at least onefirst signal characteristic and/or the first direction of transmissionmay be received from the first base station by receiving a broadcastsignal from the first base station—e.g. as described for action 511 insignaling flow 500. The at least one first signal characteristic and/orthe first direction of transmission may be received from a locationserver (e.g. LMF 120) by receiving an LPP or NPP message from thelocation server—e.g. as described for actions 512 and 513 in signalingflow 500.

In some embodiments, the location-capable device may include the firstbase station or a location server (e.g. an E-SMLC, SLP or the LMF 120),and, in such embodiments, the procedure 1000 may further include sendingthe at least one first signal characteristic and/or the first directionof transmission to the mobile device. For example, when thelocation-capable device includes the first base station, the at leastone first signal characteristic and/or the first direction oftransmission may be sent to the mobile station using broadcasting—e.g.as described for action 511 in signaling flow 500. For example, when thelocation-capable device includes the location server (e.g. LMF 120), theat least one first signal characteristic and/or the first direction oftransmission may be sent to the mobile device in an LPP or NPPmessage—e.g. as described for actions 512 and 513 in signaling flow 500.

In some embodiments, and as described previously herein, the at leastone first signal characteristic and/or the first direction oftransmission may enable or assist the mobile device to acquire andmeasure the first directional PRS and to obtain the at least one firstmeasurement of the first directional PRS (e.g. at block 1010 if themobile device is the location-capable device or prior to block 1010 ifthe location-capable device includes the first base station or alocation server). For example, the mobile device may integrate the firstdirectional PRS and other received signals using coherent ornon-coherent integration over a period of time such as the duration ofone PRS positioning occasion and may compare or correlate the integratedsignal with an expected signal that has the same at least one firstsignal characteristic, which may enable the mobile device to detect andmeasure the first directional PRS.

In some embodiments, determining the location of the mobile device atblock 1020 may be based on an observed time difference of arrival(OTDOA) position method, an angle of departure (AOD) position method, anEnhanced Cell ID (ECID) position method, or on some combination ofthese. The procedure 1000 may also include, in such embodiments,determining a presence or absence of multipath for the first directionalPRS based on the first direction of transmission and an approximatelocation for the mobile device, where determining the location of themobile device is based, at least in part, on the determined presence orabsence of multipath. For example, and as described for FIG. 4 , when apresence of multipath is determined, determining the location of themobile device at block 1020 may include disregarding (e.g. ignoring) theat least one first measurement obtained at block 1010. Conversely, andas also described for FIG. 4 , when an absence of multipath isdetermined, determining the location of the mobile device at block 1020may include using the at least one first measurement obtained at block1010 in the location determination at block 1020. The approximatelocation for the mobile device may be based, at least in part, on aserving cell for the mobile device or on a previous determination of thelocation of the mobile device based, at least in part, on the at leastone first measurement obtained at block 1010.

In some embodiments, location determination of the mobile device atblock 1020 may be implemented based on measurements by the mobile deviceof multiple directional PRS signals. Thus, in such embodiments, theprocedure 1000 may further include obtaining at least one secondmeasurement from the mobile device for a second directional PRStransmitted by a second base station in at least one cell for the secondbase station, with the second directional PRS including at least onesecond signal characteristic and a second direction of transmission, andwith the at least one second signal characteristic and the seconddirection of transmission for the second directional PRS being,respectively, different from the at least one first signalcharacteristic and the first direction of transmission for the firstdirectional PRS. In such embodiments, the procedure 1000 may alsoinclude determining the location of the mobile device based, at least inpart, on the at least one first measurement, the at least one secondmeasurement, the first direction of transmission for the firstdirectional PRS and the second direction of transmission for the seconddirectional PRS.

In some embodiments of the procedure 1000, at least one of the at leastone first signal characteristic and the first direction of transmissionfor the first directional PRS may be unique (e.g. may be different to acorresponding signal characteristic and/or corresponding direction oftransmission, respectively, for any other directional PRS transmittedwithin the at least one cell, by the first base station or by some othernearby base station).

FIG. 11 shows a schematic diagram of an example wireless node 1100, suchas a base station, access point, or server, which may be similar to, andbe configured to have a functionality similar to that, of any of thevarious nodes depicted, for example, in FIGS. 1, 2 , 4 and 5 (e.g., thegNBs 110-1 and 110-2, the ng-eNB 114, base station 202, base station410, LMF 120, components of the 5GC 140), or otherwise discussed herein(e.g. such as an E-SMLC or SLP). The wireless node 1100 may include oneor more communication modules 1110 a-n, which may be electricallycoupled to one more antennas 1116 a-n for communicating with wirelessdevices, such as, for example, the UE 105 of FIGS. 1 and 5 . Each of thecommunication modules 1110 a-1110 n may include a respective transmitter1112 a-n for sending signals (e.g., downlink messages, which may bearranged in frames, and may include directional positioning referencesignals such as those described herein) and, optionally (e.g., for nodesconfigured to receive and process uplink communications) a respectivereceiver 1114 a-n. In embodiments in which the implemented node includesboth a transmitter and a receiver, the communication module comprisingthe transmitter and receiver may be referred to as a transceiver. Thenode 1100 may also include a network interface 1120 to communicate withother network nodes via wireline means (e.g., by sending and receivingqueries and responses). For example, the node 1100 may be configured tocommunicate (e.g., via wired or wireless backhaul communication) with agateway, or other suitable device of a network, to facilitatecommunication with one or more core network nodes (e.g., any of theother nodes and elements shown in FIGS. 1 and 5 ). Additionally, and/oralternatively, communication with other network nodes may also beperformed using the communication modules 1110 a-n and/or the respectiveantennas 1116 a-n.

The node 1100 may also include other components that may be used withembodiments described herein. For example, the node 1100 may include, insome embodiments, a processor (also referred to as a controller) 1130 tomanage communications with other nodes (e.g., sending and receivingmessages), to generate communication signals (including to generatedirectional PRS signals), and to provide other related functionality,including functionality to implement the various processes and methodsdescribed herein. Thus, for example, the processor, in combination withother modules/units of the node 1100, may be configured to cause thenode 1100, when functioning as a base station (e.g. a gNB 110 or ng-eNB114), to generate a plurality of directional positioning referencesignals (PRSs) for at least one cell for the base station, with each ofthe plurality of directional PRSs including at least one signalcharacteristic and a direction of transmission, and transmit the each ofthe plurality of directional PRSs within the at least one cell, witheach of the plurality of directional PRSs being transmitted in thedirection of transmission. Similarly, for example, the processor, incombination with other modules/units of the node 1100, may be configuredto cause the node 1110, when functioning as a location-capable device,to obtain at least one first measurement from a mobile device for afirst directional positioning reference signal (PRS) transmitted by abase station in at least one cell for the base station, with the firstdirectional PRS comprising at least one first signal characteristic anda first direction of transmission, and to determine a location of themobile device based, at least in part, on the at least one firstmeasurement and the first direction of transmission.

The processor 1130 may be coupled to (or otherwise communicate with) amemory 1140, which may include one or more modules (implemented inhardware of software) to facilitate controlling the operation of thenode 1100. For example, the memory 1140 may include an applicationmodule 1146 with computer code for various applications required toperform the operation of the node 1100. For example, the processor 1130may be configured (e.g., using code provided via the application module1146, or some other module in the memory 1140) to control the operationof the antennas 1116 a-n so as to adjustably control the antennas'transmission power and phase, gain pattern, antenna direction (e.g., thedirection at which a resultant radiation beam from the antennas 1116 a-npropagates), antenna diversity, and other adjustable antenna parametersfor the antennas 1116 a-n of the node 1100. Control of the antennas 1116a-n of the node 1100, which together constitute an antenna array for thenode 1100, may allow, for example, directional PRS signals to bebeamformed and transmitted in particular directions characterized, inpart, by a direction angle and beamwidth. In some embodiments, theantennas' configuration may be controlled according to pre-storedconfiguration data provided at the time of manufacture or deployment ofthe node 1100, or according to data obtained from a remote device (suchas a central server sending data representative of the antennaconfiguration, and other operational parameters, that are to be used forthe node 1100). The wireless node 1100 may also be configured, in someimplementations, to perform location data services, or perform othertypes of services, for multiple wireless devices (clients) communicatingwith the wireless node 1100 (or communicating with a server coupled tothe wireless node 1100), and to provide location data and/or assistancedata to such multiple wireless devices.

In addition, in some embodiments, the memory 1140 may also includeneighbor relations controllers (e.g., neighbor discovery modules) 1142to manage neighbor relations (e.g., maintaining a neighbor list 1144)and to provide other related functionality. In some embodiments, thenode 1110 may also include one or more sensors (not shown) and otherdevices (e.g., cameras).

FIG. 12 illustrates a user equipment (UE) 1200 for which variousprocedures and techniques described herein can be utilized. The UE 1200may, in implementation and/or functionality, be similar to or the sameas any of the other UEs described herein, including the UE 105 depictedin FIGS. 1 and 5 and the UE 420 in FIG. 4 . Furthermore, theimplementation illustrated in FIG. 12 may also be used to implement, atleast in part, some of the nodes and devices illustrated throughout thepresent disclosure, including such nodes and devices as base stations(e.g. gNBs 110, ng-eNB 114, eNBs, etc.), location servers (e.g. LMF120), and other components and devices illustrated in and described forFIGS. 1-10 .

The UE 1200 includes a processor 1211 (or processor core) and memory1240. As described herein, the UE 1200 is configured to detect andprocess directional positioning reference signals (PRS) that are used tofacilitate location determination operations. The UE 1200 may optionallyinclude a trusted environment operably connected to the memory 1240 by apublic bus 1201 or a private bus (not shown). The UE 1200 may alsoinclude a communication interface 1220 and a wireless transceiver 1221configured to send and receive wireless signals 1223 (which may includeLTE or NR frames comprising directional PRS signals) via a wirelessantenna 1222 over a wireless network (such as the NG-RAN 135 and 5GC 140of FIG. 1 ). The wireless transceiver 1221 is connected to the bus 1201via the communication interface 1220. Here, the UE 1200 is illustratedas having a single wireless transceiver 1221. However, the UE 1200 canalternatively have multiple wireless transceivers 1221 and/or multiplewireless antennas 1222 to support multiple communication standards suchas WiFi, CDMA, Wideband CDMA (WCDMA), Long Term Evolution (LTE), 5G, NR,Bluetooth® short-range wireless communication technology, etc.

The communication interface 1220 and/or wireless transceiver 1221 maysupport operations on multiple carriers (waveform signals of differentfrequencies). Multi-carrier transmitters can transmit modulated signalssimultaneously on the multiple carriers. Each modulated signal may be aCode Division Multiple Access (CDMA) signal, a Time Division MultipleAccess (TDMA) signal, an Orthogonal Frequency Division Multiple Access(OFDMA) signal, a Single-Carrier Frequency Division Multiple Access(SC-FDMA) signal, etc. Each modulated signal may be sent on a differentcarrier and may carry pilot, control information, overhead information,data, etc.

The UE 1200 may also include a user interface 1250 (e.g., display,keyboard, touchscreen, graphical user interface (GUI)), and a SatellitePositioning System (SPS) receiver 1255 that receives SPS signals 1259(e.g., from SPS satellites) via an SPS antenna 1258 (which may be thesame antenna as wireless antenna 1222 or may be different). The SPSreceiver 1255 can communicate with a single global navigation satellitesystem (GNSS) or multiple such systems. A GNSS can include, but is notlimited to, Global Positioning System (GPS), Galileo, Glonass, Beidou(Compass), etc. SPS satellites are also referred to as satellites, spacevehicles (SVs), etc. The SPS receiver 1255 measures the SPS signals 1259and may use the measurements of the SPS signals 1259 to determine thelocation of the UE 1200. The processor 1211, memory 1240, Digital SignalProcessor (DSP) 1212 and/or specialized processor(s) (not shown) mayalso be utilized to process the SPS signals 1259, in whole or in part,and/or to compute (approximately or more precisely) the location of theUE 1200, in conjunction with SPS receiver 1255. Alternatively, the UE1200 may support transfer of the SPS measurements to a location server(e.g., E-SMLC, an LMF, such as the LMF 120 of FIG. 1 , etc.) thatcomputes the UE location instead. Storage of information from the SPSsignals 1259 or other location signals is performed using a memory 1240or registers (not shown). While only one processor 1211, one DSP 1212and one memory 1240 are shown in FIG. 12 , more than one of any, a pair,or all of these components could be used by the UE 1200. The processor1211 and DSP 1212 associated with the UE 1200 are connected to the bus1201.

The memory 1240 can include a non-transitory computer-readable storagemedium (or media) that stores functions as one or more instructions orcode. Media that can make up the memory 1240 include, but are notlimited to, RAM, ROM, FLASH, disc drives, etc. In general, the functionsstored by the memory 1240 are executed by general-purpose processor(s),such as the processor 1211, specialized processors, such as the DSP1212, etc. Thus, the memory 1240 is a processor-readable memory and/or acomputer-readable memory that stores software (programming code,instructions, etc.) configured to cause the processor(s) 1211 and/orDSP(s) 1212 to perform the functions described. Alternatively, one ormore functions of the UE 1200 may be performed in whole or in part inhardware.

A UE 1200 can estimate its current position within an associated systemusing various techniques, based on other communication entities withinview and/or information available to the UE 1200. For instance, the UE1200 can estimate its position using information obtained from basestations (e.g. gNBs, ng-eNBs), access points (APs) associated with oneor more wireless local area networks (WLANs), personal area networks(PANs) utilizing a short-range wireless communication technology such asBluetooth® wireless technology or ZIGBEE®, etc., Global NavigationSatellite System (GNSS) or other Satellite Positioning System (SPS)satellites, and/or map data obtained from a map server or other server(e.g., an LMF, an E-SMLC or SLP). In some cases, a location server,which may be an E-SMLC, SLP, Standalone Serving Mobile Location Center(SAS), or an LMF, etc., may provide assistance data to the UE 1200 toallow or assist the UE 1200 to acquire signals (e.g. signals from WLANAPs, signals from cellular base stations (including directional PRSsignals), GNSS satellites, etc.) and make location related measurementsusing these signals. The UE 1200 may then provide the measurements tothe location server to compute a location estimate (which may be knownas “UE assisted” positioning) or may compute a location estimate itself(which may be known as “UE based” positioning) based on the measurementsand possibly based also on other assistance data provided by thelocation server (e.g. such as orbital and timing data for GNSSsatellites, configuration parameters for the directional PRS signals,the precise location coordinates of WLAN APs and/or cellular basestations for use in OTDOA, AOD and/or ECID positioning, etc.)

In one embodiment, the UE 1200 may include a camera 1230 (e.g., frontand/or back facing) such as, for example, complementarymetal-oxide-semiconductor (CMOS) image sensors with appropriate lensconfigurations. Other imaging technologies such as charge-coupleddevices (CCD) and back side illuminated CMOS may be used. The camera1230 may be configured to obtain and provide image information to assistin positioning of the UE 1200. In an example, one or more external imageprocessing servers (e.g. remote servers) may be used to perform imagerecognition and provide location estimation processes. The UE 1200 mayinclude other sensors 1235 which may also be used to compute, or used toassist in computing, a location for the UE 1200. The other sensors 1235may include inertial sensors (e.g. accelerometers, gyroscopes,magnetometers, a compass, any of which may be implemented based onmicro-electro-mechanical-system (MEMS), or based on some othertechnology), as well as a barometer, thermometer, hygrometer and othersensors.

As noted, in some embodiments the UE 1200 may be configured to receive(e.g., via the wireless transceiver 1221), a first directionalpositioning reference signal (PRS) transmitted by a first base stationwithin at least one cell for the first base station, with the firstdirectional PRS comprising at least one signal characteristic and adirection of transmission. In such embodiments, the UE 1200 may furtherbe configured to obtain at least one first measurement for the firstdirectional PRS based, at least in part, on the at least one signalcharacteristic, and to facilitate location determination of the UE 1200at a location-capable device (which may include the UE 1200, and/or mayfurther include the first base station, some other base station, aremote location server, etc.) based, at least in part, on the at leastone first measurement.

Substantial variations may be made in accordance with specific desires.For example, customized hardware might also be used, and/or particularelements might be implemented in hardware, software (including portablesoftware, such as applets, etc.), or both. Further, connection to othercomputing devices such as network input/output devices may be employed.

Configurations may be described as a process which is depicted as a flowdiagram or block diagram. Although each may describe the operations as asequential process, many of the operations can be performed in parallelor concurrently. In addition, the order of the operations may berearranged. A process may have additional steps not included in thefigure. Furthermore, examples of the methods may be implemented byhardware, software, firmware, middleware, microcode, hardwaredescription languages, or any combination thereof. When implemented insoftware, firmware, middleware, or microcode, the program code or codesegments to perform the necessary tasks may be stored in anon-transitory computer-readable medium such as a storage medium.Processors may perform the described tasks.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly or conventionally understood. As usedherein, the articles “a” and “an” refer to one or to more than one(i.e., to at least one) of the grammatical object of the article. By wayof example, “an element” means one element or more than one element.“About” and/or “approximately” as used herein when referring to ameasurable value such as an amount, a temporal duration, and the like,encompasses variations of ±20% or ±10%, ±5%, or ±0.1% from the specifiedvalue, as such variations are appropriate in the context of the systems,devices, circuits, methods, and other implementations described herein.“Substantially” as used herein when referring to a measurable value suchas an amount, a temporal duration, a physical attribute (such asfrequency), and the like, also encompasses variations of ±20% or ±10%,±5%, or +0.1% from the specified value, as such variations areappropriate in the context of the systems, devices, circuits, methods,and other implementations described herein.

As used herein, including in the claims, “or” as used in a list of itemsprefaced by “at least one of” or “one or more of” indicates adisjunctive list such that, for example, a list of “at least one of A,B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B andC), or combinations with more than one feature (e.g., AA, AAB, ABBC,etc.). Also, as used herein, unless otherwise stated, a statement that afunction or operation is “based on” an item or condition means that thefunction or operation is based on the stated item or condition and maybe based on one or more items and/or conditions in addition to thestated item or condition.

As used herein, a mobile device or station (MS) refers to a device suchas a cellular or other wireless communication device, a smartphone,tablet, personal communication system (PCS) device, personal navigationdevice (PND), Personal Information Manager (PIM), Personal DigitalAssistant (PDA), laptop or other suitable mobile device which is capableof receiving wireless communication and/or navigation signals, such asnavigation positioning signals. The term “mobile station” (or “mobiledevice” or “wireless device”) is also intended to include devices whichcommunicate with a personal navigation device (PND), such as byshort-range wireless, infrared, wireline connection, or otherconnection—regardless of whether satellite signal reception, assistancedata reception, and/or position-related processing occurs at the deviceor at the PND. Also, “mobile station” is intended to include alldevices, including wireless communication devices, computers, laptops,tablet devices, etc., which are capable of communication with a server,such as via the Internet, WiFi, or other network, and to communicatewith one or more types of nodes, regardless of whether satellite signalreception, assistance data reception, and/or position-related processingoccurs at the device, at a server, or at another device or nodeassociated with the network. Any operable combination of the above arealso considered a “mobile station.” A mobile device may also be referredto as a mobile terminal, a terminal, a user equipment (UE), a device, aSecure User Plane Location Enabled Terminal (SET), a target device, atarget, or by some other name.

While some of the techniques, processes, and/or implementationspresented herein may comply with all or part of one or more standards,such techniques, processes, and/or implementations may not, in someembodiments, comply with part or all of such one or more standards.

Although particular embodiments have been disclosed herein in detail,this has been done by way of example for purposes of illustration only,and is not intended to be limiting with respect to the scope of theappended claims, which follow. In particular, it is contemplated thatvarious substitutions, alterations, and modifications may be madewithout departing from the spirit and scope of the invention as definedby the claims. Other aspects, advantages, and modifications areconsidered to be within the scope of the following claims. The claimspresented are representative of the embodiments and features disclosedherein. Other unclaimed embodiments and features are also contemplated.Accordingly, other embodiments are within the scope of the followingclaims.

What is claimed is:
 1. A first base station, for supporting positioningof a mobile device, comprising: a memory; a transmitter; and at leastone processor operably coupled to the memory and the transmitter andconfigured to: obtain at least one first signal characteristic of afirst directional positioning reference signal (PRS) to be transmittedby the first base station or to be transmitted by a second base stationnear the first base station; produce a second directional PRS that isunique relative to the first directional PRS by producing the seconddirectional PRS to have at least one second signal characteristic thatis different from the at least one first signal characteristic; andtransmit, via the transmitter, the second directional PRS.
 2. The firstbase station of claim 1, wherein the at least one processor isconfigured to produce the second directional PRS that is unique relativeto the first directional PRS by producing the second directional PRSsuch that the second directional PRS and the first directional PRS havedifferent frequencies, or different frequency shifts, or different codesequences, or different muting patterns, or different transmissiontimes, or different directions of transmission from the first basestation, or any combination of any two or more thereof.
 3. The firstbase station of claim 2, wherein the at least one processor isconfigured to produce the second directional PRS that is unique relativeto the first directional PRS by producing the second directional PRSsuch that the second directional PRS and the first directional PRS havedifferent directions of transmission from the first base station, andwherein each of the directions of transmission from the first basestation comprises a respective range of horizontal angles, or arespective range of vertical angles, or a combination thereof.
 4. Thefirst base station of claim 2, wherein the at least one processor isconfigured to produce the second directional PRS that is unique relativeto the first directional PRS by producing the second directional PRSsuch that the second directional PRS and the first directional PRS havedifferent directions of transmission from the first base station, andwherein the at least one processor is further configured to: send, viathe transmitter to the mobile device, a first direction of transmissionof the first directional PRS; and send, via the transmitter to themobile device, a second direction of transmission of the seconddirectional PRS.
 5. The first base station of claim 1, wherein the atleast one processor is configured to send, via the transmitter to themobile device, the at least one second signal characteristic of thesecond directional PRS.
 6. A method, at a first base station, forsupporting positioning of a mobile device, the method comprising:obtaining, at the first base station, at least one first signalcharacteristic of a first directional positioning reference signal (PRS)to be transmitted by the first base station or to be transmitted by asecond base station near the first base station; producing, at the firstbase station, a second directional PRS that is unique relative to thefirst directional PRS by producing the second directional PRS to have atleast one second signal characteristic that is different from the atleast one first signal characteristic; and transmitting, from the firstbase station, the second directional PRS.
 7. The method of claim 6,wherein producing the second directional PRS that is unique relative tothe first directional PRS comprises producing the second directional PRSsuch that the second directional PRS and the first directional PRS havedifferent frequencies, or different frequency shifts, or different codesequences, or different muting patterns, or different transmissiontimes, or different directions of transmission from the first basestation, or any combination of any two or more thereof.
 8. The method ofclaim 7, wherein producing the second directional PRS that is uniquerelative to the first directional PRS comprises producing the seconddirectional PRS such that the second directional PRS and the firstdirectional PRS have different directions of transmission from the firstbase station, and wherein each of the directions of transmission fromthe first base station comprises a respective range of horizontalangles, or a respective range of vertical angles, or a combinationthereof.
 9. The method of claim 7, wherein producing the seconddirectional PRS that is unique relative to the first directional PRScomprises producing the second directional PRS such that the seconddirectional PRS and the first directional PRS have different directionsof transmission from the first base station, and wherein the methodfurther comprises: sending, from the first base station to the mobiledevice, a first direction of transmission of the first directional PRS;and sending, from the first base station to the mobile device, a seconddirection of transmission of the second directional PRS.
 10. The methodof claim 6, further comprising sending, from the first base station tothe mobile device, the at least one second signal characteristic of thesecond directional PRS.
 11. A first base station, for supportingpositioning of a mobile device, comprising: means for obtaining at leastone first signal characteristic of a first directional positioningreference signal (PRS) to be transmitted by the first base station or tobe transmitted by a second base station near the first base station;means for producing a second directional PRS that is unique relative tothe first directional PRS by producing the second directional PRS tohave at least one second signal characteristic that is different fromthe at least one first signal characteristic; and means for transmittingthe second directional PRS.
 12. The first base station of claim 11,wherein the means for producing the second directional PRS that isunique relative to the first directional PRS comprise means forproducing the second directional PRS such that the second directionalPRS and the first directional PRS have different frequencies, ordifferent frequency shifts, or different code sequences, or differentmuting patterns, or different transmission times, or differentdirections of transmission from the first base station, or anycombination of any two or more thereof.
 13. The first base station ofclaim 12, wherein the means for producing the second directional PRSthat is unique relative to the first directional PRS comprise means forproducing the second directional PRS such that the second directionalPRS and the first directional PRS have different directions oftransmission from the first base station, and wherein each of thedirections of transmission from the first base station comprises arespective range of horizontal angles, or a respective range of verticalangles, or a combination thereof.
 14. The first base station of claim12, wherein the means for producing the second directional PRS that isunique relative to the first directional PRS comprise means forproducing the second directional PRS such that the second directionalPRS and the first directional PRS have different directions oftransmission from the first base station, and wherein the first basestation further comprises: means for sending, to the mobile device, afirst direction of transmission of the first directional PRS; and meansfor sending, to the mobile device, a second direction of transmission ofthe second directional PRS.
 15. The first base station of claim 11,further comprising means for sending, to the mobile device, the at leastone second signal characteristic of the second directional PRS.
 16. Anon-transitory processor-readable storage medium comprisingprocessor-readable instructions configured to cause one or moreprocessors of a first base station to support the positioning of amobile device, comprising: code for obtaining at least one first signalcharacteristic of a first directional positioning reference signal (PRS)to be transmitted by the first base station or to be transmitted by asecond base station near the first base station; code for producing asecond directional PRS that is unique relative to the first directionalPRS by producing the second directional PRS to have at least one secondsignal characteristic that is different from the at least one firstsignal characteristic; and code for transmitting the second directionalPRS.
 17. The non-transitory processor-readable storage medium of claim16, wherein the code for producing the second directional PRS that isunique relative to the first directional PRS comprises code forproducing the second directional PRS such that the second directionalPRS and the first directional PRS have different frequencies, ordifferent frequency shifts, or different code sequences, or differentmuting patterns, or different transmission times, or differentdirections of transmission from the first base station, or anycombination of any two or more thereof.
 18. The non-transitoryprocessor-readable storage medium of claim 17, wherein the code forproducing the second directional PRS that is unique relative to thefirst directional PRS comprises code for producing the seconddirectional PRS such that the second directional PRS and the firstdirectional PRS have different directions of transmission from the firstbase station, and wherein each of the directions of transmission fromthe first base station comprises a respective range of horizontalangles, or a respective range of vertical angles, or a combinationthereof.
 19. The non-transitory processor-readable storage medium ofclaim 17, wherein the code for producing the second directional PRS thatis unique relative to the first directional PRS comprises code forproducing the second directional PRS such that the second directionalPRS and the first directional PRS have different directions oftransmission from the first base station, and wherein the non-transitoryprocessor-readable storage medium further comprises: code for sending,to the mobile device, a first direction of transmission of the firstdirectional PRS; and code for sending, to the mobile device, a seconddirection of transmission of the second directional PRS.
 20. Thenon-transitory processor-readable storage medium of claim 16, furthercomprising code for sending, to the mobile device, the at least onesecond signal characteristic of the second directional PRS.